diff --git a/impl/src/main/java/com/sun/faces/application/ApplicationImpl.java b/impl/src/main/java/com/sun/faces/application/ApplicationImpl.java
index 4d7af14f85..ac6e9062b3 100644
--- a/impl/src/main/java/com/sun/faces/application/ApplicationImpl.java
+++ b/impl/src/main/java/com/sun/faces/application/ApplicationImpl.java
@@ -479,7 +479,7 @@ public Converter<?> createConverter(String converterId) {
      * @see jakarta.faces.application.Application#createConverter(Class)
      */
     @Override
-    public Converter<?> createConverter(Class<?> targetClass) {
+    public <T> Converter<T> createConverter(Class<T> targetClass) {
         return instanceFactory.createConverter(targetClass);
     }
 
diff --git a/impl/src/main/java/com/sun/faces/application/JavaFlowLoaderHelper.java b/impl/src/main/java/com/sun/faces/application/JavaFlowLoaderHelper.java
index 99d95114de..ad77144802 100644
--- a/impl/src/main/java/com/sun/faces/application/JavaFlowLoaderHelper.java
+++ b/impl/src/main/java/com/sun/faces/application/JavaFlowLoaderHelper.java
@@ -60,7 +60,7 @@ synchronized void loadFlows(FacesContext context, FlowHandler flowHandler) throw
 
         WebConfiguration config = WebConfiguration.getInstance();
         for (Producer<Flow> flowProducer : flowProducers) {
-            Flow toAdd = flowProducer.produce(beanManager.<Flow>createCreationalContext(null));
+            Flow toAdd = flowProducer.produce(beanManager.createCreationalContext(null));
             if (toAdd == null) {
                 LOGGER.log(SEVERE, "Flow producer method {0}() returned null.  Ignoring.", flowProducer.toString());
             } else {
diff --git a/impl/src/main/java/com/sun/faces/application/NamedEventManager.java b/impl/src/main/java/com/sun/faces/application/NamedEventManager.java
index 1dea5a5230..ce7b4d974a 100644
--- a/impl/src/main/java/com/sun/faces/application/NamedEventManager.java
+++ b/impl/src/main/java/com/sun/faces/application/NamedEventManager.java
@@ -38,8 +38,8 @@
  */
 public class NamedEventManager {
 
-    private Map<String, Class<? extends SystemEvent>> namedEvents = new ConcurrentHashMap<>();
-    private Map<String, Set<Class<? extends SystemEvent>>> duplicateNames = new ConcurrentHashMap<>();
+    private final Map<String, Class<? extends SystemEvent>> namedEvents = new ConcurrentHashMap<>();
+    private final Map<String, Set<Class<? extends SystemEvent>>> duplicateNames = new ConcurrentHashMap<>();
 
     public NamedEventManager() {
         namedEvents.put("jakarta.faces.event.PreRenderComponent", PreRenderComponentEvent.class);
@@ -66,7 +66,7 @@ public Class<? extends SystemEvent> getNamedEvent(String name) {
 
         if (namedEvent == null) {
             try {
-                namedEvent = loadClass(name, this);
+                namedEvent = (Class<? extends SystemEvent>) loadClass(name, this);
             } catch (ClassNotFoundException ex) {
                 throw new FacesException("An unknown event type was specified:  " + name, ex);
             }
@@ -81,12 +81,8 @@ public Class<? extends SystemEvent> getNamedEvent(String name) {
 
     public void addDuplicateName(String name, Class<? extends SystemEvent> event) {
         Class<? extends SystemEvent> registeredEvent = namedEvents.remove(name);
-        Set<Class<? extends SystemEvent>> events = duplicateNames.get(name);
+        Set<Class<? extends SystemEvent>> events = duplicateNames.computeIfAbsent(name, k -> new HashSet<>());
 
-        if (events == null) {
-            events = new HashSet<>();
-            duplicateNames.put(name, events);
-        }
         events.add(event);
 
         if (registeredEvent != null) {
diff --git a/impl/src/main/java/com/sun/faces/application/NavigationHandlerImpl.java b/impl/src/main/java/com/sun/faces/application/NavigationHandlerImpl.java
index 106ae7f8ad..71a4218d7f 100644
--- a/impl/src/main/java/com/sun/faces/application/NavigationHandlerImpl.java
+++ b/impl/src/main/java/com/sun/faces/application/NavigationHandlerImpl.java
@@ -91,7 +91,7 @@ public class NavigationHandlerImpl extends ConfigurableNavigationHandler {
 
     public static boolean isResetFlowHandlerState(FacesContext facesContext) {
 
-        Boolean obtainingNavigationCase = (Boolean) FacesContext.getCurrentInstance().getAttributes().get(RESET_FLOW_HANDLER_STATE_KEY);
+        Boolean obtainingNavigationCase = (Boolean) facesContext.getAttributes().get(RESET_FLOW_HANDLER_STATE_KEY);
         return obtainingNavigationCase != null && obtainingNavigationCase;
     }
 
@@ -256,8 +256,8 @@ public void handleNavigation(FacesContext context, String fromAction, String out
 
                         // If we are exiting all flows
                         if (caseStruct.newFlow == null) { // NOPMD
-                            parameters.put(TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME, asList(NULL_FLOW));
-                            parameters.put(FLOW_ID_REQUEST_PARAM_NAME, asList(""));
+                            parameters.put(TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME, List.of(NULL_FLOW));
+                            parameters.put(FLOW_ID_REQUEST_PARAM_NAME, List.of(""));
                             FlowHandler flowHandler = context.getApplication().getFlowHandler();
 
                             if (flowHandler instanceof FlowHandlerImpl) {
@@ -272,10 +272,10 @@ public void handleNavigation(FacesContext context, String fromAction, String out
                             if (!parameters.containsKey(TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME) || !parameters.containsKey(FLOW_ID_REQUEST_PARAM_NAME)) {
 
                                 // Overwrite both of them.
-                                List<String> toFlowDocumentIdParam = asList(caseStruct.navCase.getToFlowDocumentId());
+                                List<String> toFlowDocumentIdParam = Collections.singletonList(caseStruct.navCase.getToFlowDocumentId());
                                 parameters.put(TO_FLOW_DOCUMENT_ID_REQUEST_PARAM_NAME, toFlowDocumentIdParam);
 
-                                List<String> flowIdParam = asList(caseStruct.newFlow.getId());
+                                List<String> flowIdParam = Collections.singletonList(caseStruct.newFlow.getId());
                                 parameters.put(FLOW_ID_REQUEST_PARAM_NAME, flowIdParam);
                             }
                         }
@@ -475,9 +475,7 @@ private void initializeNavigationFromFlowNonThreadSafe(Flow toInspect) {
                 NavigationInfo info = new NavigationInfo();
                 if (!switches.isEmpty()) {
                     info.switches = new ConcurrentHashMap<>();
-                    for (Map.Entry<String, SwitchNode> cur : switches.entrySet()) {
-                        info.switches.put(cur.getKey(), cur.getValue());
-                    }
+                    info.switches.putAll(switches);
                 }
                 if (!navRules.isEmpty()) {
                     info.ruleSet = new NavigationMap();
@@ -544,7 +542,7 @@ private CaseStruct getViewId(FacesContext ctx, String fromAction, String outcome
 
         // if viewIdToTest is not null, use its value to find
         // a navigation match, otherwise look for a match
-        // based soley on the fromAction and outcome
+        // based solely on the fromAction and outcome
         CaseStruct caseStruct = null;
         Map<String, Set<NavigationCase>> navMap = getNavigationMap(ctx);
 
@@ -866,8 +864,8 @@ private CaseStruct findImplicitMatch(FacesContext context, String viewId, String
                 Map<String, Object> appMap = context.getExternalContext().getApplicationMap();
 
                 String[] queryElements = Util.split(appMap, queryString, "&amp;|&");
-                for (int i = 0, len = queryElements.length; i < len; i++) {
-                    String[] elements = Util.split(appMap, queryElements[i], "=", 2);
+                for (String queryElement : queryElements) {
+                    String[] elements = Util.split(appMap, queryElement, "=", 2);
                     if (elements.length == 2) {
                         String rightHandSide = elements[1];
                         String sanitized = null != rightHandSide && 2 < rightHandSide.length() ? rightHandSide.trim() : "";
@@ -877,19 +875,12 @@ private CaseStruct findImplicitMatch(FacesContext context, String viewId, String
                             }
                             rightHandSide = "";
                         }
+
                         if (parameters == null) {
-                            parameters = new LinkedHashMap<>(len / 2, 1.0f);
-                            List<String> values = new ArrayList<>(2);
-                            values.add(rightHandSide);
-                            parameters.put(elements[0], values);
-                        } else {
-                            List<String> values = parameters.get(elements[0]);
-                            if (values == null) {
-                                values = new ArrayList<>(2);
-                                parameters.put(elements[0], values);
-                            }
-                            values.add(rightHandSide);
+                            parameters = new LinkedHashMap<>(queryElements.length / 2, 1.0f);
                         }
+
+                        parameters.computeIfAbsent(elements[0], k -> new ArrayList<>(2)).add(rightHandSide);
                     }
                 }
             }
diff --git a/impl/src/main/java/com/sun/faces/application/PropertyEditorHelper.java b/impl/src/main/java/com/sun/faces/application/PropertyEditorHelper.java
index 588dfd2b5b..f432f0de4d 100644
--- a/impl/src/main/java/com/sun/faces/application/PropertyEditorHelper.java
+++ b/impl/src/main/java/com/sun/faces/application/PropertyEditorHelper.java
@@ -35,7 +35,7 @@
  */
 public class PropertyEditorHelper {
 
-    private Application app;
+    private final Application app;
 
     public PropertyEditorHelper(Application app) {
         this.app = app;
@@ -49,7 +49,7 @@ public PropertyEditorHelper(Application app) {
      */
     public Object convertToObject(Class<?> targetClass, String textValue) {
         UIComponent component = getComponent();
-        Converter converter = app.createConverter(targetClass);
+        Converter<?> converter = app.createConverter(targetClass);
         if (null == converter) {
             // PENDING(edburns): I18N
             FacesException e = new FacesException(
diff --git a/impl/src/main/java/com/sun/faces/application/applicationimpl/InstanceFactory.java b/impl/src/main/java/com/sun/faces/application/applicationimpl/InstanceFactory.java
index 7617eec378..c7ffdee0d6 100644
--- a/impl/src/main/java/com/sun/faces/application/applicationimpl/InstanceFactory.java
+++ b/impl/src/main/java/com/sun/faces/application/applicationimpl/InstanceFactory.java
@@ -435,9 +435,9 @@ public Converter<?> createConverter(String converterId) {
     /*
      * @see jakarta.faces.application.Application#createConverter(Class)
      */
-    public Converter createConverter(Class<?> targetClass) {
+    public <T> Converter<T> createConverter(Class<T> targetClass) {
         notNull("targetClass", targetClass);
-        Converter returnVal = null;
+        Converter<T> returnVal = null;
 
         BeanManager beanManager = getBeanManager();
         returnVal = CdiUtils.createConverter(beanManager, targetClass);
diff --git a/impl/src/main/java/com/sun/faces/application/applicationimpl/events/ComponentSystemEventHelper.java b/impl/src/main/java/com/sun/faces/application/applicationimpl/events/ComponentSystemEventHelper.java
index 46fe5f1ad9..1b857ead67 100644
--- a/impl/src/main/java/com/sun/faces/application/applicationimpl/events/ComponentSystemEventHelper.java
+++ b/impl/src/main/java/com/sun/faces/application/applicationimpl/events/ComponentSystemEventHelper.java
@@ -17,16 +17,18 @@
 package com.sun.faces.application.applicationimpl.events;
 
 import com.sun.faces.util.Cache;
-import com.sun.faces.util.Cache.Factory;
+
 
 import jakarta.faces.event.SystemEvent;
 
+import java.util.function.Function;
+
 /**
  * Utility class for dealing with {@link jakarta.faces.component.UIComponent} events.
  */
 public class ComponentSystemEventHelper {
 
-    private Cache<Class<?>, Cache<Class<? extends SystemEvent>, EventInfo>> sourceCache;
+    private final Cache<Class<?>, Cache<Class<? extends SystemEvent>, EventInfo>> sourceCache;
 
     // -------------------------------------------------------- Constructors
 
@@ -34,8 +36,8 @@ public ComponentSystemEventHelper() {
 
         // Initialize the 'sources' cache for, ahem, readability...
         // ~generics++
-        Factory<Class<?>, Cache<Class<? extends SystemEvent>, EventInfo>> eventCacheFactory = sourceClass -> {
-            Factory<Class<? extends SystemEvent>, EventInfo> eventInfoFactory = systemEventClass -> new EventInfo(systemEventClass, sourceClass);
+        Cache.Factory<Class<?>, Cache<Class<? extends SystemEvent>, EventInfo>> eventCacheFactory = sourceClass -> {
+            Cache.Factory<Class<? extends SystemEvent>, EventInfo> eventInfoFactory = systemEventClass -> new EventInfo(systemEventClass, sourceClass);
             return new Cache<>(eventInfoFactory);
         };
         sourceCache = new Cache<>(eventCacheFactory);
diff --git a/impl/src/main/java/com/sun/faces/application/resource/ResourceCache.java b/impl/src/main/java/com/sun/faces/application/resource/ResourceCache.java
index c722cbb5e0..7f104f2d52 100644
--- a/impl/src/main/java/com/sun/faces/application/resource/ResourceCache.java
+++ b/impl/src/main/java/com/sun/faces/application/resource/ResourceCache.java
@@ -51,12 +51,12 @@ public class ResourceCache {
     /**
      * The <code>ResourceInfo<code> cache.
      */
-    private MultiKeyConcurrentHashMap<Object, ResourceInfoCheckPeriodProxy> resourceCache;
+    private final MultiKeyConcurrentHashMap<Object, ResourceInfoCheckPeriodProxy> resourceCache;
 
     /**
      * Resource check period in minutes.
      */
-    private long checkPeriod;
+    private final long checkPeriod;
 
     // ------------------------------------------------------------ Constructors
 
@@ -99,7 +99,7 @@ public ResourceInfo add(ResourceInfo info, List<String> contracts) {
         if (LOGGER.isLoggable(FINE)) {
             LOGGER.log(FINE, "Caching ResourceInfo: {0}", info.toString());
         }
-        ResourceInfoCheckPeriodProxy proxy = resourceCache.putIfAbsent(info.name, info.libraryName, info.localePrefix, new ArrayList(contracts),
+        ResourceInfoCheckPeriodProxy proxy = resourceCache.putIfAbsent(info.name, info.libraryName, info.localePrefix, new ArrayList<>(contracts),
                 new ResourceInfoCheckPeriodProxy(info, checkPeriod));
         return proxy != null ? proxy.getResourceInfo() : null;
 
@@ -153,7 +153,7 @@ private static String getServletContextIdentifier(ServletContext context) {
 
     private static final class ResourceInfoCheckPeriodProxy {
 
-        private ResourceInfo resourceInfo;
+        private final ResourceInfo resourceInfo;
         private Long checkTime;
 
         // -------------------------------------------------------- Constructors
diff --git a/impl/src/main/java/com/sun/faces/application/view/FaceletFullStateManagementStrategy.java b/impl/src/main/java/com/sun/faces/application/view/FaceletFullStateManagementStrategy.java
index 96b7b8be92..655a32b090 100644
--- a/impl/src/main/java/com/sun/faces/application/view/FaceletFullStateManagementStrategy.java
+++ b/impl/src/main/java/com/sun/faces/application/view/FaceletFullStateManagementStrategy.java
@@ -87,12 +87,12 @@ public class FaceletFullStateManagementStrategy extends StateManagementStrategy
     /**
      * Stores the class map.
      */
-    private Map<String, Class<?>> classMap;
+    private final Map<String, Class<?>> classMap;
 
     /**
      * Are we in development mode.
      */
-    private boolean isDevelopmentMode;
+    private final boolean isDevelopmentMode;
 
     /**
      * Constructor.
@@ -348,10 +348,10 @@ private void restoreComponentState(final FacesContext context, final HashMap<Str
      *
      * @param context the Faces context.
      * @param stateContext the state context.
-     * @param stateMap the state.
-     * @param viewRoot the view root.
+     * @param state the state.
+     *
      */
-    private void restoreDynamicActions(FacesContext context, StateContext stateContext, HashMap<String, Object> state) {
+    private void restoreDynamicActions(FacesContext context, StateContext stateContext, Map<String, Object> state) {
         if (LOGGER.isLoggable(FINEST)) {
             LOGGER.finest("FaceletFullStateManagementStrategy.restoreDynamicActions");
         }
@@ -602,7 +602,7 @@ private Object saveComponentState(FacesContext context) {
                 Object stateObj;
                 if (!component.isTransient()) {
                     if (stateContext.componentAddedDynamically(component)) {
-                        component.getAttributes().put(DYNAMIC_COMPONENT, new Integer(getProperChildIndex(component)));
+                        component.getAttributes().put(DYNAMIC_COMPONENT, getProperChildIndex(component));
                         stateObj = new StateHolderSaver(finalContext, component);
                     } else {
                         stateObj = component.saveState(finalContext);
@@ -628,7 +628,7 @@ private Object saveComponentState(FacesContext context) {
      *
      * @param context the Faces context.
      * @param stateContext the state context.
-     * @param stateMap the state.
+     *
      */
     private void saveDynamicActions(FacesContext context, StateContext stateContext, UIViewRoot viewRoot) {
         if (LOGGER.isLoggable(FINEST)) {
@@ -636,7 +636,7 @@ private void saveDynamicActions(FacesContext context, StateContext stateContext,
         }
 
         List<ComponentStruct> actions = stateContext.getDynamicActions();
-        HashMap<String, UIComponent> componentMap = stateContext.getDynamicComponents();
+        Map<String, UIComponent> componentMap = stateContext.getDynamicComponents();
 
         if (actions != null) {
             List<Object> savedActions = new ArrayList<>(actions.size());
@@ -673,7 +673,7 @@ public Object saveView(FacesContext context) {
          */
         Util.checkIdUniqueness(context, viewRoot, new HashSet<>(viewRoot.getChildCount() << 1));
 
-        /**
+        /*
          * Save the dynamic actions.
          */
         StateContext stateContext = StateContext.getStateContext(context);
diff --git a/impl/src/main/java/com/sun/faces/application/view/FaceletPartialStateManagementStrategy.java b/impl/src/main/java/com/sun/faces/application/view/FaceletPartialStateManagementStrategy.java
index 29e763978f..2cd49b6c09 100644
--- a/impl/src/main/java/com/sun/faces/application/view/FaceletPartialStateManagementStrategy.java
+++ b/impl/src/main/java/com/sun/faces/application/view/FaceletPartialStateManagementStrategy.java
@@ -392,7 +392,7 @@ private void saveDynamicActions(FacesContext context, StateContext stateContext,
         }
 
         List<ComponentStruct> actions = stateContext.getDynamicActions();
-        HashMap<String, UIComponent> componentMap = stateContext.getDynamicComponents();
+        Map<String, UIComponent> componentMap = stateContext.getDynamicComponents();
 
         if (actions != null) {
             List<Object> savedActions = new ArrayList<>(actions.size());
diff --git a/impl/src/main/java/com/sun/faces/application/view/FaceletViewHandlingStrategy.java b/impl/src/main/java/com/sun/faces/application/view/FaceletViewHandlingStrategy.java
index 2324424349..3401c0187a 100644
--- a/impl/src/main/java/com/sun/faces/application/view/FaceletViewHandlingStrategy.java
+++ b/impl/src/main/java/com/sun/faces/application/view/FaceletViewHandlingStrategy.java
@@ -930,7 +930,7 @@ protected void handleRenderException(FacesContext context, Exception e) throws I
         // Always log
         if (LOGGER.isLoggable(SEVERE)) {
             UIViewRoot root = context.getViewRoot();
-            StringBuffer sb = new StringBuffer(64);
+            StringBuilder sb = new StringBuilder(64);
             sb.append("Error Rendering View");
             if (root != null) {
                 sb.append('[');
@@ -1148,7 +1148,7 @@ private boolean handlesByPrefixOrSuffix(String viewId) {
         // If there's no extensions array or prefixes array, then assume defaults.
         // .xhtml extension is handled by the FaceletViewHandler
         if (extensionsArray == null && prefixesArray == null) {
-            return isMatchedWithFaceletsSuffix(viewId) ? true : viewId.endsWith(DEFAULT_FACELETS_SUFFIX);
+            return isMatchedWithFaceletsSuffix(viewId) || viewId.endsWith(DEFAULT_FACELETS_SUFFIX);
         }
 
         if (extensionsArray != null) {
@@ -1231,7 +1231,7 @@ private void retargetHandler(FacesContext context, AttachedObjectHandler handler
     private static final class MethodMetadataIterator implements Iterable<CompCompInterfaceMethodMetadata>, Iterator<CompCompInterfaceMethodMetadata> {
 
         private final PropertyDescriptor[] descriptors;
-        private FacesContext context;
+        private final FacesContext context;
         private int curIndex = -1;
 
         // -------------------------------------------------------- Constructors
@@ -1364,7 +1364,7 @@ public String getTargetAttributeName(FacesContext ctx) {
         public boolean isRequired(FacesContext ctx) {
 
             ValueExpression rd = (ValueExpression) propertyDescriptor.getValue("required");
-            return rd != null ? Boolean.valueOf(rd.getValue(ctx.getELContext()).toString()) : false;
+            return rd != null && Boolean.parseBoolean(rd.getValue(ctx.getELContext()).toString());
 
         }
 
@@ -1400,8 +1400,8 @@ public String getName() {
      */
     private static final class MethodRetargetHandlerManager {
 
-        private Map<String, MethodRetargetHandler> handlerMap = new HashMap<>(4, 1.0f);
-        private MethodRetargetHandler arbitraryHandler = new ArbitraryMethodRegargetHandler();
+        private final Map<String, MethodRetargetHandler> handlerMap = new HashMap<>(4, 1.0f);
+        private final MethodRetargetHandler arbitraryHandler = new ArbitraryMethodRegargetHandler();
 
         // -------------------------------------------------------- Constructors
 
@@ -1914,11 +1914,11 @@ private Stream<String> mapIfNeeded(Stream<String> views, ViewVisitOption... opti
             return views;
         }
 
-        return views.map(view -> toImplicitOutcome(view));
+        return views.map(this::toImplicitOutcome);
     }
 
     private boolean returnAsImplicitOutCome(ViewVisitOption... options) {
-        return stream(options).filter(option -> option == RETURN_AS_MINIMAL_IMPLICIT_OUTCOME).findAny().isPresent();
+        return stream(options).anyMatch(option -> option == RETURN_AS_MINIMAL_IMPLICIT_OUTCOME);
     }
 
     private String toImplicitOutcome(String viewId) {
diff --git a/impl/src/main/java/com/sun/faces/cdi/CdiConverter.java b/impl/src/main/java/com/sun/faces/cdi/CdiConverter.java
index 43695f8be4..ffb07cb9fb 100644
--- a/impl/src/main/java/com/sun/faces/cdi/CdiConverter.java
+++ b/impl/src/main/java/com/sun/faces/cdi/CdiConverter.java
@@ -24,7 +24,7 @@
 /**
  * A delegate to the CDI managed converter.
  */
-public class CdiConverter implements Converter, StateHolder {
+public class CdiConverter<T> implements Converter<T>, StateHolder {
 
     /**
      * Stores the converter-id (if any).
@@ -34,12 +34,12 @@ public class CdiConverter implements Converter, StateHolder {
     /**
      * Stores a transient reference to the CDI managed converter.
      */
-    private transient Converter delegate;
+    private transient Converter<T> delegate;
 
     /**
      * Stores the for-class (if any).
      */
-    private Class<?> forClass;
+    private Class<T> forClass;
 
     /**
      * Constructor.
@@ -54,7 +54,7 @@ public CdiConverter() {
      * @param forClass the for class.
      * @param delegate the delegate.
      */
-    public CdiConverter(String converterId, Class forClass, Converter delegate) {
+    public CdiConverter(String converterId, Class<T> forClass, Converter<T> delegate) {
         this.converterId = converterId;
         this.forClass = forClass;
         this.delegate = delegate;
@@ -69,8 +69,8 @@ public CdiConverter(String converterId, Class forClass, Converter delegate) {
      * @return the object.
      */
     @Override
-    public Object getAsObject(FacesContext facesContext, UIComponent component, String value) {
-        return getDelegate(facesContext).getAsObject(facesContext, component, value);
+    public T getAsObject(FacesContext facesContext, UIComponent component, String value) {
+        return (T) getDelegate(facesContext).getAsObject(facesContext, component, value);
     }
 
     /**
@@ -82,8 +82,8 @@ public Object getAsObject(FacesContext facesContext, UIComponent component, Stri
      * @return the string.
      */
     @Override
-    public String getAsString(FacesContext facesContext, UIComponent component, Object value) {
-        return getDelegate(facesContext).getAsString(facesContext, component, value);
+    public String getAsString(FacesContext facesContext, UIComponent component, T value) {
+        return ((Converter<T>)getDelegate(facesContext)).getAsString(facesContext, component, value);
     }
 
     /**
@@ -107,7 +107,7 @@ public Object saveState(FacesContext facesContext) {
     public void restoreState(FacesContext facesContext, Object state) {
         Object[] stateArray = (Object[]) state;
         converterId = (String) stateArray[0];
-        forClass = (Class<?>) stateArray[1];
+        forClass = (Class<T>) stateArray[1];
     }
 
     /**
@@ -139,9 +139,9 @@ public void setTransient(boolean transientValue) {
      * @param facesContext the Faces context.
      * @return the delegate.
      */
-    private Converter getDelegate(FacesContext facesContext) {
+    private Converter<T> getDelegate(FacesContext facesContext) {
         if (delegate == null) {
-            if (!converterId.equals("")) {
+            if (!"".equals(converterId)) {
                 delegate = facesContext.getApplication().createConverter(converterId);
             } else {
                 delegate = facesContext.getApplication().createConverter(forClass);
diff --git a/impl/src/main/java/com/sun/faces/cdi/CdiUtils.java b/impl/src/main/java/com/sun/faces/cdi/CdiUtils.java
index a79cd59eb9..4436182c96 100644
--- a/impl/src/main/java/com/sun/faces/cdi/CdiUtils.java
+++ b/impl/src/main/java/com/sun/faces/cdi/CdiUtils.java
@@ -106,19 +106,19 @@ public static Converter<?> createConverter(BeanManager beanManager, String value
      * @param forClass the for class.
      * @return the converter, or null if we could not match one.
      */
-    public static Converter<?> createConverter(BeanManager beanManager, Class<?> forClass) {
-        Converter<?> managedConverter = null;
+    public static <T> Converter<T> createConverter(BeanManager beanManager, Class<T> forClass) {
+        Converter<T> managedConverter = null;
 
         for (Class<?> forClassOrSuperclass = forClass; managedConverter == null && forClassOrSuperclass != null
                 && forClassOrSuperclass != Object.class; forClassOrSuperclass = forClassOrSuperclass.getSuperclass()) {
-            managedConverter = createConverter(beanManager, FacesConverter.Literal.of("", forClassOrSuperclass, true));
+            managedConverter = (Converter<T>) createConverter(beanManager, FacesConverter.Literal.of("", forClassOrSuperclass, true));
         }
 
         if (managedConverter != null) {
             ApplicationAssociate associate = ApplicationAssociate.getCurrentInstance();
             associate.getAnnotationManager().applyConverterAnnotations(FacesContext.getCurrentInstance(), managedConverter); // #4913
 
-            return new CdiConverter("", forClass, managedConverter);
+            return new CdiConverter<>("", forClass, managedConverter);
         }
 
         return null;
@@ -261,10 +261,7 @@ private static String getBeanName(Bean<?> bean) {
 
         String className = bean.getBeanClass().getSimpleName();
 
-        return new StringBuilder()
-            .append(Character.toLowerCase(className.charAt(0)))
-            .append(className.substring(1))
-            .toString();
+        return Character.toLowerCase(className.charAt(0)) + className.substring(1);
     }
 
     /**
diff --git a/impl/src/main/java/com/sun/faces/component/CompositeComponentStackManager.java b/impl/src/main/java/com/sun/faces/component/CompositeComponentStackManager.java
index 203382e111..8e440e0b5b 100644
--- a/impl/src/main/java/com/sun/faces/component/CompositeComponentStackManager.java
+++ b/impl/src/main/java/com/sun/faces/component/CompositeComponentStackManager.java
@@ -371,7 +371,7 @@ private final class TreeCreationStackHandler extends BaseStackHandler {
         @Override
         public void pop() {
 
-            Stack s = getStack(false);
+            Stack<UIComponent> s = getStack(false);
             if (s != null && !stack.isEmpty()) {
                 stack.pop();
                 if (stack.isEmpty()) {
diff --git a/impl/src/main/java/com/sun/faces/component/PassthroughElement.java b/impl/src/main/java/com/sun/faces/component/PassthroughElement.java
index 98ef132021..004f7f8cec 100644
--- a/impl/src/main/java/com/sun/faces/component/PassthroughElement.java
+++ b/impl/src/main/java/com/sun/faces/component/PassthroughElement.java
@@ -376,7 +376,7 @@ private void handleAttribute(String name, Object value) {
         List<String> setAttributes = (List<String>) getAttributes().get("jakarta.faces.component.UIComponentBase.attributesThatAreSet");
         if (setAttributes == null) {
             String cname = this.getClass().getName();
-            if (cname != null && cname.startsWith(OPTIMIZED_PACKAGE)) {
+            if (cname.startsWith(OPTIMIZED_PACKAGE)) {
                 setAttributes = new ArrayList<>(6);
                 getAttributes().put("jakarta.faces.component.UIComponentBase.attributesThatAreSet", setAttributes);
             }
diff --git a/impl/src/main/java/com/sun/faces/component/search/CompositeSearchKeywordResolver.java b/impl/src/main/java/com/sun/faces/component/search/CompositeSearchKeywordResolver.java
index 9f8deb680f..c1c86e2a13 100644
--- a/impl/src/main/java/com/sun/faces/component/search/CompositeSearchKeywordResolver.java
+++ b/impl/src/main/java/com/sun/faces/component/search/CompositeSearchKeywordResolver.java
@@ -46,8 +46,7 @@ public void add(SearchKeywordResolver searchKeywordResolver) {
     public void resolve(SearchKeywordContext context, UIComponent current, String keyword) {
         context.setKeywordResolved(false);
 
-        for (int i = 0; i < resolvers.size(); i++) {
-            SearchKeywordResolver resolver = resolvers.get(i);
+        for (SearchKeywordResolver resolver : resolvers) {
             if (resolver.isResolverForKeyword(context.getSearchExpressionContext(), keyword)) {
                 resolver.resolve(context, current, keyword);
                 if (context.isKeywordResolved()) {
@@ -59,8 +58,7 @@ public void resolve(SearchKeywordContext context, UIComponent current, String ke
 
     @Override
     public boolean isResolverForKeyword(SearchExpressionContext searchExpressionContext, String keyword) {
-        for (int i = 0; i < resolvers.size(); i++) {
-            SearchKeywordResolver resolver = resolvers.get(i);
+        for (SearchKeywordResolver resolver : resolvers) {
             if (resolver.isResolverForKeyword(searchExpressionContext, keyword)) {
                 return true;
             }
@@ -71,8 +69,7 @@ public boolean isResolverForKeyword(SearchExpressionContext searchExpressionCont
 
     @Override
     public boolean isPassthrough(SearchExpressionContext searchExpressionContext, String keyword) {
-        for (int i = 0; i < resolvers.size(); i++) {
-            SearchKeywordResolver resolver = resolvers.get(i);
+        for (SearchKeywordResolver resolver : resolvers) {
             if (resolver.isResolverForKeyword(searchExpressionContext, keyword)) {
                 return resolver.isPassthrough(searchExpressionContext, keyword);
             }
@@ -83,8 +80,7 @@ public boolean isPassthrough(SearchExpressionContext searchExpressionContext, St
 
     @Override
     public boolean isLeaf(SearchExpressionContext searchExpressionContext, String keyword) {
-        for (int i = 0; i < resolvers.size(); i++) {
-            SearchKeywordResolver resolver = resolvers.get(i);
+        for (SearchKeywordResolver resolver : resolvers) {
             if (resolver.isResolverForKeyword(searchExpressionContext, keyword)) {
                 return resolver.isLeaf(searchExpressionContext, keyword);
             }
diff --git a/impl/src/main/java/com/sun/faces/component/search/SearchExpressionHandlerImpl.java b/impl/src/main/java/com/sun/faces/component/search/SearchExpressionHandlerImpl.java
index f12fb58297..5950fa0e4e 100644
--- a/impl/src/main/java/com/sun/faces/component/search/SearchExpressionHandlerImpl.java
+++ b/impl/src/main/java/com/sun/faces/component/search/SearchExpressionHandlerImpl.java
@@ -35,9 +35,7 @@ public class SearchExpressionHandlerImpl extends SearchExpressionHandler {
 
     protected void addHint(SearchExpressionContext searchExpressionContext, SearchExpressionHint hint) {
         // It is a Set already
-        if (!searchExpressionContext.getExpressionHints().contains(hint)) {
-            searchExpressionContext.getExpressionHints().add(hint);
-        }
+        searchExpressionContext.getExpressionHints().add(hint);
     }
 
     @Override
@@ -340,6 +338,7 @@ public String[] splitExpressions(FacesContext context, String expressions) {
                 for (char separator : separators) {
                     if (c == separator) {
                         isSeparator = true;
+                        break;
                     }
                 }
 
@@ -362,7 +361,7 @@ public String[] splitExpressions(FacesContext context, String expressions) {
         // lets not forget about part after the separator
         tokens.add(buffer.toString());
 
-        return tokens.toArray(new String[tokens.size()]);
+        return tokens.toArray(new String[0]);
     }
 
     @Override
diff --git a/impl/src/main/java/com/sun/faces/component/validator/ComponentValidators.java b/impl/src/main/java/com/sun/faces/component/validator/ComponentValidators.java
index dc897b7186..ef5b6bca4c 100644
--- a/impl/src/main/java/com/sun/faces/component/validator/ComponentValidators.java
+++ b/impl/src/main/java/com/sun/faces/component/validator/ComponentValidators.java
@@ -16,12 +16,7 @@
 
 package com.sun.faces.component.validator;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 
 import com.sun.faces.facelets.tag.faces.ComponentSupport;
 import com.sun.faces.util.RequestStateManager;
@@ -137,23 +132,17 @@ public void addValidators(FacesContext ctx, EditableValueHolder editableValueHol
         Map<String, String> defaultValidatorInfo = application.getDefaultValidatorInfo();
         Set<String> keySet = defaultValidatorInfo.keySet();
 
-        List<String> validatorIds = new ArrayList<>(keySet.size());
-        for (String key : keySet) {
-            validatorIds.add(key);
-        }
+        // the same order of keySet ... defaultValidatorInfo is a LinkedHashMap ...
+        Collection<String> validatorIds = new LinkedHashSet<>(keySet);
 
         Set<String> disabledIds = (Set<String>) RequestStateManager.remove(ctx, RequestStateManager.DISABLED_VALIDATORS);
         int count = validatorStack.size();
         for (int i = count - 1; i >= 0; i--) {
             ValidatorInfo info = validatorStack.get(i);
             if (!info.isEnabled() || disabledIds != null && disabledIds.contains(info.getValidatorId())) {
-                if (validatorIds.contains(info.getValidatorId())) {
-                    validatorIds.remove(info.getValidatorId());
-                }
+                validatorIds.remove(info.getValidatorId());
             } else {
-                if (!validatorIds.contains(info.getValidatorId())) {
-                    validatorIds.add(info.getValidatorId());
-                }
+                validatorIds.add(info.getValidatorId());
             }
         }
 
@@ -209,11 +198,11 @@ private static void addValidatorsToComponent(FacesContext ctx, Collection<String
 
         Application application = ctx.getApplication();
         Map<String, String> defaultValidatorInfo = application.getDefaultValidatorInfo();
-        Validator[] validators = editableValueHolder.getValidators();
+        Validator<?>[] validators = editableValueHolder.getValidators();
         // check to make sure that Validator instances haven't already
         // been added.
         for (Map.Entry<String, String> defaultValidator : defaultValidatorInfo.entrySet()) {
-            for (Validator validator : validators) {
+            for (Validator<?> validator : validators) {
                 if (defaultValidator.getValue().equals(validator.getClass().getName())) {
                     validatorIds.remove(defaultValidator.getKey());
                     break;
@@ -222,9 +211,9 @@ private static void addValidatorsToComponent(FacesContext ctx, Collection<String
         }
 
         // we now have the complete List of Validator IDs to add to the
-        // target EditablValueHolder
+        // target EditableValueHolder
         for (String id : validatorIds) {
-            Validator v = application.createValidator(id);
+            Validator<?> v = application.createValidator(id);
             // work backwards up the stack of ValidatorInfo to find the
             // nearest matching ValidatorInfo to apply attributes
             if (validatorStack != null) {
@@ -248,10 +237,10 @@ private static void addValidatorsToComponent(FacesContext ctx, Collection<String
      */
     public static class ValidatorInfo {
 
-        private String validatorId;
-        private boolean enabled;
-        private ValidatorHandler owner;
-        private FaceletContext ctx;
+        private final String validatorId;
+        private final boolean enabled;
+        private final ValidatorHandler owner;
+        private final FaceletContext ctx;
 
         // ------------------------------------------------------------ Constructors
 
@@ -278,7 +267,7 @@ public boolean isEnabled() {
 
         }
 
-        public void applyAttributes(Validator v) {
+        public void applyAttributes(Validator<?> v) {
 
             owner.setAttributes(ctx, v);
 
diff --git a/impl/src/main/java/com/sun/faces/component/visit/FullVisitContext.java b/impl/src/main/java/com/sun/faces/component/visit/FullVisitContext.java
index 34880854bb..00b2b522ec 100644
--- a/impl/src/main/java/com/sun/faces/component/visit/FullVisitContext.java
+++ b/impl/src/main/java/com/sun/faces/component/visit/FullVisitContext.java
@@ -126,8 +126,8 @@ public VisitResult invokeVisitCallback(UIComponent component, VisitCallback call
     }
 
     // The FacesContext for this request
-    private FacesContext facesContext;
+    private final FacesContext facesContext;
 
     // Our visit hints
-    private Set<VisitHint> hints;
+    private final Set<VisitHint> hints;
 }
diff --git a/impl/src/main/java/com/sun/faces/component/visit/PartialVisitContext.java b/impl/src/main/java/com/sun/faces/component/visit/PartialVisitContext.java
index ff6e7d9386..94fcfdf9b7 100644
--- a/impl/src/main/java/com/sun/faces/component/visit/PartialVisitContext.java
+++ b/impl/src/main/java/com/sun/faces/component/visit/PartialVisitContext.java
@@ -309,12 +309,7 @@ private void addSubtreeClientId(String clientId) {
                 // NamingContainer client id. If not, create the
                 // Collection for this NamingContainer client id and
                 // stash it away in our map
-                Collection<String> c = subtreeClientIds.get(namingContainerClientId);
-
-                if (c == null) {
-                    c = new ArrayList<>();
-                    subtreeClientIds.put(namingContainerClientId, c);
-                }
+                Collection<String> c = subtreeClientIds.computeIfAbsent(namingContainerClientId, k -> new ArrayList<>());
 
                 // Stash away the client id
                 c.add(clientId);
@@ -373,7 +368,7 @@ public boolean add(E o) {
             return added;
         }
 
-        private Collection<E> wrapped;
+        private final Collection<E> wrapped;
     }
 
     // Little proxy iterator implementation used by CollectionProxy
@@ -405,7 +400,7 @@ public void remove() {
             wrapped.remove();
         }
 
-        private Iterator<E> wrapped;
+        private final Iterator<E> wrapped;
 
         private E current = null;
     }
@@ -426,8 +421,8 @@ public void remove() {
     private Map<String, Collection<String>> subtreeClientIds;
 
     // The FacesContext for this request
-    private FacesContext facesContext;
+    private final FacesContext facesContext;
 
     // Our visit hints
-    private Set<VisitHint> hints;
+    private final Set<VisitHint> hints;
 }
diff --git a/impl/src/main/java/com/sun/faces/component/visit/VisitContextFactoryImpl.java b/impl/src/main/java/com/sun/faces/component/visit/VisitContextFactoryImpl.java
index 614c8e0ee8..753633cb01 100644
--- a/impl/src/main/java/com/sun/faces/component/visit/VisitContextFactoryImpl.java
+++ b/impl/src/main/java/com/sun/faces/component/visit/VisitContextFactoryImpl.java
@@ -37,7 +37,7 @@ public VisitContextFactoryImpl() {
 
     @Override
     public VisitContext getVisitContext(FacesContext context, Collection<String> ids, Set<VisitHint> hints) {
-        VisitContext result = null;
+        VisitContext result;
 
         // If ids null (not empty), we create a FullVisitContext.
         // Otherwise, we create a PartialVisitContext. Note that
diff --git a/impl/src/main/java/com/sun/faces/config/ConfigManager.java b/impl/src/main/java/com/sun/faces/config/ConfigManager.java
index 99591b0bb5..93a1d2e584 100644
--- a/impl/src/main/java/com/sun/faces/config/ConfigManager.java
+++ b/impl/src/main/java/com/sun/faces/config/ConfigManager.java
@@ -128,10 +128,9 @@ public class ConfigManager {
      * when the application is destroyed.
      * </p>
      */
-    private List<ServletContext> initializedContexts = new CopyOnWriteArrayList<>();
+    private final List<ServletContext> initializedContexts = new CopyOnWriteArrayList<>();
 
-    private final List<ConfigProcessor> configProcessors = unmodifiableList(
-            asList(
+    private final List<ConfigProcessor> configProcessors = List.of(
                 new FactoryConfigProcessor(),
                 new LifecycleConfigProcessor(),
                 new ApplicationConfigProcessor(),
@@ -144,7 +143,7 @@ public class ConfigManager {
                 new FacesConfigExtensionProcessor(),
                 new ProtectedViewsConfigProcessor(),
                 new FacesFlowDefinitionConfigProcessor(),
-                new ResourceLibraryContractsConfigProcessor()));
+                new ResourceLibraryContractsConfigProcessor());
 
     /**
      * <p>
@@ -152,8 +151,8 @@ public class ConfigManager {
      * Mojarra, and two other providers to satisfy the requirements of the specification.
      * </p>
      */
-    private final List<ConfigurationResourceProvider> facesConfigProviders = unmodifiableList(
-            asList(new MetaInfFacesConfigResourceProvider(), new WebAppFlowConfigResourceProvider(), new WebFacesConfigResourceProvider()));
+    private final List<ConfigurationResourceProvider> facesConfigProviders = List.of(
+            new MetaInfFacesConfigResourceProvider(), new WebAppFlowConfigResourceProvider(), new WebFacesConfigResourceProvider());
 
     /**
      * <p>
@@ -161,8 +160,8 @@ public class ConfigManager {
      * Mojarra, and one other providers to satisfy the requirements of the specification.
      * </p>
      */
-    private final List<ConfigurationResourceProvider> facesletsTagLibConfigProviders = unmodifiableList(
-            asList(new MetaInfFaceletTaglibraryConfigProvider(), new WebFaceletTaglibResourceProvider()));
+    private final List<ConfigurationResourceProvider> facesletsTagLibConfigProviders = List.of(
+            new MetaInfFaceletTaglibraryConfigProvider(), new WebFaceletTaglibResourceProvider());
 
     /**
      * <p>
@@ -260,7 +259,7 @@ public void initialize(ServletContext servletContext, InitFacesContext facesCont
                 // from each document.
 
                 DocumentInfo[] facesDocuments2 = facesDocuments;
-                configProcessors.subList(0, 3).stream().forEach(e -> {
+                configProcessors.subList(0, 3).forEach(e -> {
                     try {
                         e.process(servletContext, facesContext, facesDocuments2);
                     } catch (Exception e2) {
@@ -275,7 +274,7 @@ public void initialize(ServletContext servletContext, InitFacesContext facesCont
                 ThreadContext threadContext = getThreadContext(containerConnector);
                 Object parentWebContext = threadContext != null ? threadContext.getParentWebContext() : null;
 
-                configProcessors.subList(3, configProcessors.size()).stream().forEach(e -> {
+                configProcessors.subList(3, configProcessors.size()).forEach(e -> {
 
                     long currentThreadId = Thread.currentThread().getId();
 
@@ -403,7 +402,7 @@ private List<ApplicationConfigurationPopulator> getConfigPopulators() {
 
         configPopulators.add(new MojarraRuntimePopulator());
 
-        ServiceLoader.load(ApplicationConfigurationPopulator.class).forEach(e -> configPopulators.add(e));
+        ServiceLoader.load(ApplicationConfigurationPopulator.class).forEach(configPopulators::add);
 
         return configPopulators;
     }
@@ -477,7 +476,7 @@ private void releaseFactories() {
      * @param servletContext the <code>ServletContext</code> for the application that needs to be removed
      */
     public void destroy(ServletContext servletContext, FacesContext facesContext) {
-        configProcessors.stream().forEach(e -> e.destroy(servletContext, facesContext));
+        configProcessors.forEach(e -> e.destroy(servletContext, facesContext));
         initializedContexts.remove(servletContext);
     }
 
diff --git a/impl/src/main/java/com/sun/faces/config/ConfigureListener.java b/impl/src/main/java/com/sun/faces/config/ConfigureListener.java
index fa975e1f73..545f2f36d6 100644
--- a/impl/src/main/java/com/sun/faces/config/ConfigureListener.java
+++ b/impl/src/main/java/com/sun/faces/config/ConfigureListener.java
@@ -702,7 +702,7 @@ public WebConfigResourceMonitor(ServletContext servletContext, Collection<URI> u
                     monitors.add(new Monitor(uri));
                 } catch (IOException ioe) {
                     LOGGER.log(SEVERE, () -> "Unable to setup resource monitor for " + uri.toString() + ".  Resource will not be monitored for changes.");
-                    LOGGER.log(FINE, ioe, () -> ioe.toString());
+                    LOGGER.log(FINE, ioe, ioe::toString);
                 }
             }
 
diff --git a/impl/src/main/java/com/sun/faces/config/FaceletsConfiguration.java b/impl/src/main/java/com/sun/faces/config/FaceletsConfiguration.java
index bd7b289636..ddb6fc793a 100644
--- a/impl/src/main/java/com/sun/faces/config/FaceletsConfiguration.java
+++ b/impl/src/main/java/com/sun/faces/config/FaceletsConfiguration.java
@@ -36,11 +36,11 @@ public class FaceletsConfiguration {
 
 //    private static final String CONSUME_COMMENTS_ATTRIBUTE_NAME = "com.sun.faces.config.ConsumeComments";
 
-    private static Pattern EXTENSION_PATTERN = Pattern.compile("\\.[^/]+$");
+    private static final Pattern EXTENSION_PATTERN = Pattern.compile("\\.[^/]+$");
 
-    private WebConfiguration config;
+    private final WebConfiguration config;
 
-    private Map<String, String> faceletsProcessingMappings;
+    private final Map<String, String> faceletsProcessingMappings;
 
     public FaceletsConfiguration(WebConfiguration config) {
         this.config = config;
diff --git a/impl/src/main/java/com/sun/faces/config/InitFacesContext.java b/impl/src/main/java/com/sun/faces/config/InitFacesContext.java
index 96c3312dec..d2f88c00c5 100644
--- a/impl/src/main/java/com/sun/faces/config/InitFacesContext.java
+++ b/impl/src/main/java/com/sun/faces/config/InitFacesContext.java
@@ -51,7 +51,7 @@
  */
 public class InitFacesContext extends NoOpFacesContext {
 
-    private static Logger LOGGER = FacesLogger.CONFIG.getLogger();
+    private static final Logger LOGGER = FacesLogger.CONFIG.getLogger();
     private static final String INIT_FACES_CONTEXT_ATTR_NAME = RIConstants.FACES_PREFIX + "InitFacesContext";
 
     private ServletContextAdapter servletContextAdapter;
diff --git a/impl/src/main/java/com/sun/faces/config/Verifier.java b/impl/src/main/java/com/sun/faces/config/Verifier.java
index dc35d7a28c..8afdd89ec1 100644
--- a/impl/src/main/java/com/sun/faces/config/Verifier.java
+++ b/impl/src/main/java/com/sun/faces/config/Verifier.java
@@ -46,7 +46,7 @@ public enum ObjectType {
     /**
      * Container for any messages that may be queued.
      */
-    private List<String> messages;
+    private final List<String> messages;
 
     // ------------------------------------------------------- Constructors
 
@@ -126,7 +126,7 @@ public void validateObject(ObjectType type, String className, Class<?> assignabl
 
         if (c != null) {
             try {
-                Constructor ctor = c.getConstructor(RIConstants.EMPTY_CLASS_ARGS);
+                Constructor<?> ctor = c.getConstructor(RIConstants.EMPTY_CLASS_ARGS);
                 if (!Modifier.isPublic(ctor.getModifiers())) {
                     messages.add(MessageUtils.getExceptionMessageString(MessageUtils.VERIFIER_CTOR_NOT_PUBLIC_ID, type, className));
                 }
diff --git a/impl/src/main/java/com/sun/faces/config/WebConfiguration.java b/impl/src/main/java/com/sun/faces/config/WebConfiguration.java
index 012bb5cd16..ae798b3ed4 100644
--- a/impl/src/main/java/com/sun/faces/config/WebConfiguration.java
+++ b/impl/src/main/java/com/sun/faces/config/WebConfiguration.java
@@ -95,19 +95,19 @@ public class WebConfiguration {
     // Logging level. Defaults to FINE
     private Level loggingLevel = Level.FINE;
 
-    private Map<BooleanWebContextInitParameter, Boolean> booleanContextParameters = new EnumMap<>(BooleanWebContextInitParameter.class);
+    private final Map<BooleanWebContextInitParameter, Boolean> booleanContextParameters = new EnumMap<>(BooleanWebContextInitParameter.class);
 
-    private Map<WebContextInitParameter, String> contextParameters = new EnumMap<>(WebContextInitParameter.class);
+    private final Map<WebContextInitParameter, String> contextParameters = new EnumMap<>(WebContextInitParameter.class);
 
-    private Map<WebContextInitParameter, Map<String, String>> facesConfigParameters = new EnumMap<>(WebContextInitParameter.class);
+    private final Map<WebContextInitParameter, Map<String, String>> facesConfigParameters = new EnumMap<>(WebContextInitParameter.class);
 
-    private Map<WebEnvironmentEntry, String> envEntries = new EnumMap<>(WebEnvironmentEntry.class);
+    private final Map<WebEnvironmentEntry, String> envEntries = new EnumMap<>(WebEnvironmentEntry.class);
 
-    private Map<WebContextInitParameter, String[]> cachedListParams;
+    private final Map<WebContextInitParameter, String[]> cachedListParams;
 
-    private Set<String> setParams = new HashSet<>();
+    private final Set<String> setParams = new HashSet<>();
 
-    private ServletContext servletContext;
+    private final ServletContext servletContext;
 
     private ArrayList<DeferredLoggingAction> deferredLoggingActions;
 
@@ -315,7 +315,7 @@ public void overrideContextInitParameter(BooleanWebContextInitParameter param, b
             return;
         }
 
-        boolean oldVal = booleanContextParameters.put(param, value);
+        boolean oldVal = Boolean.TRUE.equals(booleanContextParameters.put(param, value));
         if (LOGGER.isLoggable(FINE) && oldVal != value) {
             LOGGER.log(FINE, "Overriding init parameter {0}.  Changing from {1} to {2}.", new Object[] { param.getQualifiedName(), oldVal, value });
         }
@@ -462,8 +462,7 @@ private void discoverResourceLibraryContracts() {
                 }
             }
         } else {
-            contractsToExpose = new ArrayList<>();
-            contractsToExpose.addAll(foundContracts);
+            contractsToExpose = new ArrayList<>(foundContracts);
             contractMappings.put("*", contractsToExpose);
         }
         extContex.getApplicationMap().put(FaceletViewHandlingStrategy.RESOURCE_LIBRARY_CONTRACT_DATA_STRUCTURE_KEY, contractMappings);
@@ -513,7 +512,7 @@ private boolean isValueValid(BooleanWebContextInitParameter param, String value)
      */
     private void processBooleanParameters(ServletContext servletContext, String contextName) {
 
-        // process boolean contxt parameters
+        // process boolean context parameters
         for (BooleanWebContextInitParameter param : BooleanWebContextInitParameter.values()) {
             String strValue = servletContext.getInitParameter(param.getQualifiedName());
             boolean value;
@@ -534,12 +533,12 @@ private void processBooleanParameters(ServletContext servletContext, String cont
 
                 if (alternate != null) {
                     if (isValueValid(param, strValue)) {
-                        value = Boolean.valueOf(strValue);
+                        value = Boolean.parseBoolean(strValue);
                     } else {
                         value = param.getDefaultValue();
                     }
 
-                    if (LOGGER.isLoggable(Level.INFO) && alternate != null) {
+                    if (LOGGER.isLoggable(Level.INFO)) {
                         queueLoggingAction(new DeferredBooleanParameterLoggingAction(param, Level.INFO,
                                 value ? "faces.config.webconfig.configinfo.reset.enabled" : "faces.config.webconfig.configinfo.reset.disabled",
                                 new Object[] { contextName, alternate.getQualifiedName() }));
@@ -555,7 +554,7 @@ private void processBooleanParameters(ServletContext servletContext, String cont
                     value = param.getDefaultValue();
                 } else {
                     if (isValueValid(param, strValue)) {
-                        value = Boolean.valueOf(strValue);
+                        value = Boolean.parseBoolean(strValue);
                     } else {
                         value = param.getDefaultValue();
                     }
@@ -586,8 +585,8 @@ private void processBooleanParameters(ServletContext servletContext, String cont
      * @param servletContext the ServletContext of interest
      */
     private void initSetList(ServletContext servletContext) {
-        for (Enumeration e = servletContext.getInitParameterNames(); e.hasMoreElements();) {
-            String name = e.nextElement().toString();
+        for (Enumeration<String> e = servletContext.getInitParameterNames(); e.hasMoreElements();) {
+            String name = e.nextElement();
             if (name.startsWith("com.sun.faces") || name.startsWith("jakarta.faces")) {
                 setParams.add(name);
             }
@@ -677,9 +676,9 @@ private void processJndiEntries(String contextName) {
             initialContext = new InitialContext();
         } catch (NoClassDefFoundError nde) {
             // On google app engine InitialContext is forbidden to use and GAE throws NoClassDefFoundError
-            LOGGER.log(FINE, nde, () -> nde.toString());
+            LOGGER.log(FINE, nde, nde::toString);
         } catch (NamingException ne) {
-            LOGGER.log(Level.WARNING, ne, () -> ne.toString());
+            LOGGER.log(Level.WARNING, ne, ne::toString);
         }
 
         if (initialContext != null) {
@@ -691,7 +690,7 @@ private void processJndiEntries(String contextName) {
                 try {
                     value = (String) initialContext.lookup(entryName);
                 } catch (NamingException root) {
-                    LOGGER.log(Level.FINE, () -> root.toString());
+                    LOGGER.log(Level.FINE, root::toString);
                 }
 
                 if (value != null) {
@@ -778,11 +777,11 @@ public enum WebContextInitParameter {
         WebAppContractsDirectory(ResourceHandler.WEBAPP_CONTRACTS_DIRECTORY_PARAM_NAME, "/contracts"),
         ;
 
-        private String defaultValue;
-        private String qualifiedName;
-        private WebContextInitParameter alternate;
-        private boolean deprecated;
-        private DeprecationLoggingStrategy loggingStrategy;
+        private final String defaultValue;
+        private final String qualifiedName;
+        private final WebContextInitParameter alternate;
+        private final boolean deprecated;
+        private final DeprecationLoggingStrategy loggingStrategy;
 
         // ---------------------------------------------------------- Public Methods
 
@@ -888,12 +887,12 @@ public enum BooleanWebContextInitParameter {
         UseFaceletsID("com.sun.faces.useFaceletsID",false),
         ;
 
-        private BooleanWebContextInitParameter alternate;
+        private final BooleanWebContextInitParameter alternate;
 
-        private String qualifiedName;
-        private boolean defaultValue;
-        private boolean deprecated;
-        private DeprecationLoggingStrategy loggingStrategy;
+        private final String qualifiedName;
+        private final boolean defaultValue;
+        private final boolean deprecated;
+        private final DeprecationLoggingStrategy loggingStrategy;
 
         // ---------------------------------------------------------- Public Methods
 
@@ -952,7 +951,7 @@ public enum WebEnvironmentEntry {
         ProjectStage(jakarta.faces.application.ProjectStage.PROJECT_STAGE_JNDI_NAME);
 
         private static final String JNDI_PREFIX = "java:comp/env/";
-        private String qualifiedName;
+        private final String qualifiedName;
 
         // ---------------------------------------------------------- Public Methods
 
@@ -1017,10 +1016,10 @@ private interface DeferredLoggingAction {
 
     private class DeferredParameterLoggingAction implements DeferredLoggingAction {
 
-        private WebContextInitParameter parameter;
-        private Level loggingLevel;
-        private String logKey;
-        private Object[] params;
+        private final WebContextInitParameter parameter;
+        private final Level loggingLevel;
+        private final String logKey;
+        private final Object[] params;
 
         DeferredParameterLoggingAction(WebContextInitParameter parameter, Level loggingLevel, String logKey, Object[] params) {
 
@@ -1047,10 +1046,10 @@ public void log() {
 
     private class DeferredBooleanParameterLoggingAction implements DeferredLoggingAction {
 
-        private BooleanWebContextInitParameter parameter;
-        private Level loggingLevel;
-        private String logKey;
-        private Object[] params;
+        private final BooleanWebContextInitParameter parameter;
+        private final Level loggingLevel;
+        private final String logKey;
+        private final Object[] params;
 
         DeferredBooleanParameterLoggingAction(BooleanWebContextInitParameter parameter, Level loggingLevel, String logKey, Object[] params) {
             this.parameter = parameter;
diff --git a/impl/src/main/java/com/sun/faces/config/configprovider/BaseWebConfigResourceProvider.java b/impl/src/main/java/com/sun/faces/config/configprovider/BaseWebConfigResourceProvider.java
index 3d11fb7eda..70615c9edc 100644
--- a/impl/src/main/java/com/sun/faces/config/configprovider/BaseWebConfigResourceProvider.java
+++ b/impl/src/main/java/com/sun/faces/config/configprovider/BaseWebConfigResourceProvider.java
@@ -86,7 +86,7 @@ protected URI getContextURLForPath(ServletContext context, String path) {
         try {
             URL url = context.getResource(path);
             if (url != null) {
-                return new URI(url.toExternalForm().replaceAll(" ", "%20"));
+                return new URI(url.toExternalForm().replace(" ", "%20"));
             }
         } catch (MalformedURLException | URISyntaxException mue) {
             throw new FacesException(mue);
diff --git a/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFaceletTaglibraryConfigProvider.java b/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFaceletTaglibraryConfigProvider.java
index 2900ef7e95..abd9739a79 100644
--- a/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFaceletTaglibraryConfigProvider.java
+++ b/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFaceletTaglibraryConfigProvider.java
@@ -64,7 +64,7 @@ public Collection<URI> getResources(ServletContext context) {
             }
 
             return resourceURLs.stream()
-                               .map(url -> transformToURI(url))
+                               .map(this::transformToURI)
                                .collect(toList());
 
         } catch (IOException ioe) {
@@ -76,7 +76,7 @@ public Collection<URI> getResources(ServletContext context) {
 
     private URI transformToURI(URL url) {
         try {
-            return new URI(url.toExternalForm().replaceAll(" ", "%20"));
+            return new URI(url.toExternalForm().replace(" ", "%20"));
         } catch (URISyntaxException ex) {
             throw new FacesException(ex);
         }
diff --git a/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFacesConfigResourceProvider.java b/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFacesConfigResourceProvider.java
index 40501e2257..e0c0504b89 100644
--- a/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFacesConfigResourceProvider.java
+++ b/impl/src/main/java/com/sun/faces/config/configprovider/MetaInfFacesConfigResourceProvider.java
@@ -98,11 +98,7 @@ public Collection<URI> getResources(ServletContext context) {
                         }
                     }
 
-                    Set<URI> uris = sortedJarMap.get(jarName);
-                    if (uris == null) {
-                        uris = new HashSet<>();
-                        sortedJarMap.put(jarName, uris);
-                    }
+                    Set<URI> uris = sortedJarMap.computeIfAbsent(jarName, k -> new HashSet<>());
                     uris.add(uri);
                 } else {
                     unsortedResourceList.add(0, uri);
@@ -131,7 +127,7 @@ private Collection<URI> loadURLs(ServletContext context) throws IOException {
         try {
             for (Enumeration<URL> e = Util.getCurrentLoader(this).getResources(META_INF_RESOURCES); e.hasMoreElements();) {
                 String urlString = e.nextElement().toExternalForm();
-                urlString = urlString.replaceAll(" ", "%20");
+                urlString = urlString.replace(" ", "%20");
                 urls.add(new URI(urlString));
             }
             URL[] urlArray = Classpath.search("META-INF/", FACES_CONFIG_EXTENSION);
@@ -141,7 +137,7 @@ private Collection<URI> loadURLs(ServletContext context) throws IOException {
                 urls.add(new URI(urlString));
             }
             // special case for finding taglib files in WEB-INF/classes/META-INF
-            Set paths = context.getResourcePaths(WEB_INF_CLASSES);
+            Set<String> paths = context.getResourcePaths(WEB_INF_CLASSES);
             if (paths != null) {
                 for (Object path : paths) {
                     String p = path.toString();
diff --git a/impl/src/main/java/com/sun/faces/config/configprovider/WebAppFlowConfigResourceProvider.java b/impl/src/main/java/com/sun/faces/config/configprovider/WebAppFlowConfigResourceProvider.java
index 8a6a6c349d..1c5d9864bd 100644
--- a/impl/src/main/java/com/sun/faces/config/configprovider/WebAppFlowConfigResourceProvider.java
+++ b/impl/src/main/java/com/sun/faces/config/configprovider/WebAppFlowConfigResourceProvider.java
@@ -74,7 +74,7 @@ public Collection<URI> getResources(ServletContext context) {
             }
         }
 
-        return null == list ? Collections.EMPTY_LIST : list;
+        return null == list ? Collections.emptyList() : list;
 
     }
 
diff --git a/impl/src/main/java/com/sun/faces/config/initfacescontext/NoOpFacesContext.java b/impl/src/main/java/com/sun/faces/config/initfacescontext/NoOpFacesContext.java
index 01e7ca954c..0dec948301 100644
--- a/impl/src/main/java/com/sun/faces/config/initfacescontext/NoOpFacesContext.java
+++ b/impl/src/main/java/com/sun/faces/config/initfacescontext/NoOpFacesContext.java
@@ -16,8 +16,10 @@
 
 package com.sun.faces.config.initfacescontext;
 
+import static java.util.Collections.emptyIterator;
 import static java.util.Collections.emptyList;
 
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
@@ -38,8 +40,7 @@ public Lifecycle getLifecycle() {
 
     @Override
     public Iterator<String> getClientIdsWithMessages() {
-        List<String> list = emptyList();
-        return list.iterator();
+        return emptyIterator();
     }
 
     @Override
@@ -49,8 +50,7 @@ public FacesMessage.Severity getMaximumSeverity() {
 
     @Override
     public Iterator<FacesMessage> getMessages() {
-        List<FacesMessage> list = emptyList();
-        return list.iterator();
+        return emptyIterator();
     }
 
     @Override
diff --git a/impl/src/main/java/com/sun/faces/config/initfacescontext/ServletContextAdapter.java b/impl/src/main/java/com/sun/faces/config/initfacescontext/ServletContextAdapter.java
index b8bd6de4b9..7d5185908c 100644
--- a/impl/src/main/java/com/sun/faces/config/initfacescontext/ServletContextAdapter.java
+++ b/impl/src/main/java/com/sun/faces/config/initfacescontext/ServletContextAdapter.java
@@ -165,17 +165,17 @@ public String getRequestContextPath() {
 
     @Override
     public Map<String, Object> getRequestCookieMap() {
-        return unmodifiableMap(emptyMap());
+        return emptyMap();
     }
 
     @Override
     public Map<String, String> getRequestHeaderMap() {
-        return unmodifiableMap(emptyMap());
+        return emptyMap();
     }
 
     @Override
     public Map<String, String[]> getRequestHeaderValuesMap() {
-        return unmodifiableMap(emptyMap());
+        return emptyMap();
     }
 
     @Override
@@ -195,17 +195,17 @@ public Map<String, Object> getRequestMap() {
 
     @Override
     public Map<String, String> getRequestParameterMap() {
-        return unmodifiableMap(emptyMap());
+        return emptyMap();
     }
 
     @Override
     public Iterator<String> getRequestParameterNames() {
-        return Collections.<String>emptyList().iterator();
+        return Collections.emptyIterator();
     }
 
     @Override
     public Map<String, String[]> getRequestParameterValuesMap() {
-        return unmodifiableMap(emptyMap());
+        return emptyMap();
     }
 
     @Override
diff --git a/impl/src/main/java/com/sun/faces/config/manager/DbfFactory.java b/impl/src/main/java/com/sun/faces/config/manager/DbfFactory.java
index 4e9011d019..be7249ae93 100644
--- a/impl/src/main/java/com/sun/faces/config/manager/DbfFactory.java
+++ b/impl/src/main/java/com/sun/faces/config/manager/DbfFactory.java
@@ -103,7 +103,7 @@ private static class FacesEntityResolver extends DefaultHandler implements LSRes
          * Contains mapping between grammar name and the local URL to the
          * physical resource.
          */
-        private HashMap<String, String> entities = new HashMap<>(12, 1.0f);
+        private final HashMap<String, String> entities = new HashMap<>(12, 1.0f);
 
         // -------------------------------------------------------- Constructors
 
@@ -129,7 +129,7 @@ public FacesEntityResolver() {
                             try {
                                 schemaUrl = schemaFile.toURI().toURL();
                             } catch (MalformedURLException mue) {
-                                LOGGER.log(SEVERE, mue, () -> mue.toString());
+                                LOGGER.log(SEVERE, mue, mue::toString);
                             }
 
                             if (schemaUrl == null) {
@@ -353,7 +353,7 @@ private static Map<FacesSchema, Schema> getSchemaMap(ServletContext servletConte
 
         if (schemaMap == null) {
             synchronized (servletContext) {
-                schemaMap = synchronizedMap(new EnumMap<FacesSchema, Schema>(FacesSchema.class));
+                schemaMap = synchronizedMap(new EnumMap<>(FacesSchema.class));
                 servletContext.setAttribute(SCHEMA_MAP, schemaMap);
             }
         }
diff --git a/impl/src/main/java/com/sun/faces/config/manager/Documents.java b/impl/src/main/java/com/sun/faces/config/manager/Documents.java
index 1c946b6ad7..450972de58 100644
--- a/impl/src/main/java/com/sun/faces/config/manager/Documents.java
+++ b/impl/src/main/java/com/sun/faces/config/manager/Documents.java
@@ -117,7 +117,7 @@ public static DocumentInfo[] getXMLDocuments(ServletContext servletContext, List
             }
         }
 
-        return docs.toArray(new DocumentInfo[docs.size()]);
+        return docs.toArray(new DocumentInfo[0]);
     }
 
     public static List<DocumentInfo> getProgrammaticDocuments(List<ApplicationConfigurationPopulator> configPopulators) throws ParserConfigurationException {
@@ -192,7 +192,7 @@ public static DocumentInfo[] sortDocuments(DocumentInfo[] facesDocuments, FacesC
                 list.add(new DocumentOrderingWrapper(facesDocuments[i]));
             }
 
-            DocumentOrderingWrapper[] ordering = list.toArray(new DocumentOrderingWrapper[list.size()]);
+            DocumentOrderingWrapper[] ordering = list.toArray(new DocumentOrderingWrapper[0]);
             if (absoluteOrdering == null) {
                 DocumentOrderingWrapper.sort(ordering);
 
diff --git a/impl/src/main/java/com/sun/faces/config/manager/FacesConfigInfo.java b/impl/src/main/java/com/sun/faces/config/manager/FacesConfigInfo.java
index 8686434fe3..cc04c296bb 100644
--- a/impl/src/main/java/com/sun/faces/config/manager/FacesConfigInfo.java
+++ b/impl/src/main/java/com/sun/faces/config/manager/FacesConfigInfo.java
@@ -48,8 +48,8 @@ public class FacesConfigInfo {
     private static final String OTHERS = "others";
 
     private double version = 2.0;
-    private boolean isWebInfFacesConfig;
-    private boolean metadataComplete;
+    private final boolean isWebInfFacesConfig;
+    private final boolean metadataComplete;
     private List<String> absoluteOrdering;
 
     // -------------------------------------------------------- Constructors
@@ -141,7 +141,7 @@ private boolean isMetadataComplete(Document document) {
 
         if (isVersionGreaterOrEqual(2.0)) {
             String metadataComplete = document.getDocumentElement().getAttributeNS(document.getNamespaceURI(), "metadata-complete");
-            return metadataComplete != null ? Boolean.valueOf(metadataComplete) : false;
+            return metadataComplete != null && Boolean.parseBoolean(metadataComplete);
         }
 
         // not a 2.0 application, so annotation processing will not occur
diff --git a/impl/src/main/java/com/sun/faces/context/AjaxNoAjaxExceptionHandler.java b/impl/src/main/java/com/sun/faces/context/AjaxNoAjaxExceptionHandler.java
index c397d3a113..b1690966ac 100644
--- a/impl/src/main/java/com/sun/faces/context/AjaxNoAjaxExceptionHandler.java
+++ b/impl/src/main/java/com/sun/faces/context/AjaxNoAjaxExceptionHandler.java
@@ -22,7 +22,7 @@
 
 public class AjaxNoAjaxExceptionHandler extends ExceptionHandlerWrapper {
 
-    private AjaxExceptionHandlerImpl ajaxExceptionHandlerImpl;
+    private final AjaxExceptionHandlerImpl ajaxExceptionHandlerImpl;
 
     public AjaxNoAjaxExceptionHandler(AjaxExceptionHandlerImpl ajaxExceptionHandlerImpl, ExceptionHandlerImpl exceptionHandlerImpl) {
         super(exceptionHandlerImpl);
diff --git a/impl/src/main/java/com/sun/faces/context/ApplicationMap.java b/impl/src/main/java/com/sun/faces/context/ApplicationMap.java
index aa18cc0ecb..eda242697e 100644
--- a/impl/src/main/java/com/sun/faces/context/ApplicationMap.java
+++ b/impl/src/main/java/com/sun/faces/context/ApplicationMap.java
@@ -45,18 +45,15 @@ public Object getContext() {
 
     @Override
     public void clear() {
-        for (Enumeration e = servletContext.getAttributeNames(); e.hasMoreElements();) {
-            servletContext.removeAttribute((String) e.nextElement());
+        for (Enumeration<String> e = servletContext.getAttributeNames(); e.hasMoreElements();) {
+            servletContext.removeAttribute(e.nextElement());
         }
     }
 
     // Supported by maps if overridden
     @Override
-    public void putAll(Map t) {
-        for (Iterator i = t.entrySet().iterator(); i.hasNext();) {
-            Map.Entry entry = (Map.Entry) i.next();
-            servletContext.setAttribute((String) entry.getKey(), entry.getValue());
-        }
+    public void putAll(Map<? extends String, ?> map) {
+        map.forEach(servletContext::setAttribute);
     }
 
     @Override
@@ -91,14 +88,14 @@ public boolean containsKey(Object key) {
 
     @Override
     public boolean equals(Object obj) {
-        return !(obj == null || !(obj instanceof ApplicationMap)) && super.equals(obj);
+        return obj instanceof ApplicationMap && super.equals(obj);
     }
 
     @Override
     public int hashCode() {
         int hashCode = 7 * servletContext.hashCode();
-        for (Iterator i = entrySet().iterator(); i.hasNext();) {
-            hashCode += i.next().hashCode();
+        for (Map.Entry<String, Object> stringObjectEntry : entrySet()) {
+            hashCode += stringObjectEntry.hashCode();
         }
         return hashCode;
     }
diff --git a/impl/src/main/java/com/sun/faces/context/BaseContextMap.java b/impl/src/main/java/com/sun/faces/context/BaseContextMap.java
index 972ffce797..c17bf21eb3 100644
--- a/impl/src/main/java/com/sun/faces/context/BaseContextMap.java
+++ b/impl/src/main/java/com/sun/faces/context/BaseContextMap.java
@@ -16,14 +16,7 @@
 
 package com.sun.faces.context;
 
-import java.util.AbstractCollection;
-import java.util.AbstractMap;
-import java.util.AbstractSet;
-import java.util.Collection;
-import java.util.Enumeration;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 
 /**
  * <p>
@@ -46,7 +39,7 @@ public void clear() {
 
     // Supported by maps if overridden
     @Override
-    public void putAll(Map t) {
+    public void putAll(Map<? extends String, ? extends V> map) {
         throw new UnsupportedOperationException();
     }
 
@@ -95,8 +88,8 @@ protected boolean removeValue(Object value) {
             return false;
         }
         if (containsValue(value)) {
-            for (Iterator i = entrySet().iterator(); i.hasNext();) {
-                Map.Entry e = (Map.Entry) i.next();
+            for (Iterator<Map.Entry<String, V>> i = entrySet().iterator(); i.hasNext();) {
+                Map.Entry<String, V> e = i.next();
                 if (value.equals(e.getValue())) {
                     valueRemoved = remove(e.getKey()) != null;
                 }
@@ -135,7 +128,7 @@ public Iterator<Map.Entry<String, V>> iterator() {
 
         @Override
         public boolean remove(Object o) {
-            return o instanceof Map.Entry && removeKey(((Map.Entry) o).getKey());
+            return o instanceof Map.Entry && removeKey(((Map.Entry<?, ?>) o).getKey());
         }
 
     }
@@ -163,7 +156,7 @@ class ValueCollection extends AbstractCollection<V> {
         @Override
         public int size() {
             int size = 0;
-            for (Iterator i = iterator(); i.hasNext(); size++) {
+            for (Iterator<V> i = iterator(); i.hasNext(); size++) {
                 i.next();
             }
             return size;
@@ -180,7 +173,7 @@ public boolean remove(Object o) {
         }
     }
 
-    abstract class BaseIterator<E> implements Iterator<E> {
+    abstract static class BaseIterator<E> implements Iterator<E> {
 
         protected Enumeration e;
         protected String currentKey;
@@ -304,7 +297,7 @@ public int hashCode() {
 
         @Override
         public boolean equals(Object obj) {
-            if (obj == null || !(obj instanceof Map.Entry)) {
+            if ( !(obj instanceof Map.Entry) ) {
                 return false;
             }
 
@@ -312,12 +305,7 @@ public boolean equals(Object obj) {
             Object inputKey = input.getKey();
             Object inputValue = input.getValue();
 
-            if (inputKey == key || inputKey != null && inputKey.equals(key)) {
-                if (inputValue == value || inputValue != null && inputValue.equals(value)) {
-                    return true;
-                }
-            }
-            return false;
+            return Objects.equals(inputKey, key) && Objects.equals(inputValue, value);
         }
     }
 
diff --git a/impl/src/main/java/com/sun/faces/context/ContextParam.java b/impl/src/main/java/com/sun/faces/context/ContextParam.java
index e4cd1830f8..ae787f3b7b 100644
--- a/impl/src/main/java/com/sun/faces/context/ContextParam.java
+++ b/impl/src/main/java/com/sun/faces/context/ContextParam.java
@@ -54,7 +54,7 @@ public enum ContextParam {
     /**
      * Constructor.
      */
-    ContextParam(String name, Class type, Object defaultValue) {
+    ContextParam(String name, Class<?> type, Object defaultValue) {
         this.name = name;
         this.type = type;
         this.defaultValue = defaultValue;
@@ -76,7 +76,7 @@ public Object getDefaultValue() {
      * @param clazz the class.
      * @return the default value.
      */
-    public <T extends Object> T getDefaultValue(Class<T> clazz) {
+    public <T> T getDefaultValue(Class<T> clazz) {
         return clazz.cast(defaultValue);
     }
 
@@ -94,7 +94,7 @@ public String getName() {
      *
      * @return the type.
      */
-    public Class getType() {
+    public Class<?> getType() {
         return type;
     }
 }
diff --git a/impl/src/main/java/com/sun/faces/context/ContextParamUtils.java b/impl/src/main/java/com/sun/faces/context/ContextParamUtils.java
index 96bba227c4..15043b4d93 100644
--- a/impl/src/main/java/com/sun/faces/context/ContextParamUtils.java
+++ b/impl/src/main/java/com/sun/faces/context/ContextParamUtils.java
@@ -58,7 +58,7 @@ public static Object getValue(ServletContext servletContext, ContextParam contex
      * @param clazz the class.
      * @return the value.
      */
-    public static <T extends Object> T getValue(ServletContext servletContext, ContextParam contextParam, Class<T> clazz) {
+    public static <T> T getValue(ServletContext servletContext, ContextParam contextParam, Class<T> clazz) {
         return clazz.cast(getValue(servletContext, contextParam));
     }
 }
diff --git a/impl/src/main/java/com/sun/faces/context/ExceptionHandlerImpl.java b/impl/src/main/java/com/sun/faces/context/ExceptionHandlerImpl.java
index 708ef57385..551c6b9961 100644
--- a/impl/src/main/java/com/sun/faces/context/ExceptionHandlerImpl.java
+++ b/impl/src/main/java/com/sun/faces/context/ExceptionHandlerImpl.java
@@ -56,7 +56,7 @@ public class ExceptionHandlerImpl extends ExceptionHandler {
     private LinkedList<ExceptionQueuedEvent> unhandledExceptions;
     private LinkedList<ExceptionQueuedEvent> handledExceptions;
     private ExceptionQueuedEvent handled;
-    private boolean errorPagePresent;
+    private final boolean errorPagePresent;
 
     // ------------------------------------------------------------ Constructors
 
@@ -209,7 +209,7 @@ private void throwIt(FacesContext ctx, FacesException fe) {
                 LOGGER.log(Level.INFO, "Exception when handling error trying to reset the response.", wrapped);
             }
         }
-        if (null != wrapped && wrapped instanceof FacesFileNotFoundException) {
+        if (wrapped instanceof FacesFileNotFoundException) {
             extContext.setResponseStatus(404);
         } else {
             extContext.setResponseStatus(500);
@@ -225,7 +225,7 @@ private void throwIt(FacesContext ctx, FacesException fe) {
             if (isDevelopment) {
                 // store the view root where the exception occurred into the
                 // request scope so that the error page can display that component
-                // tree and not the one rendering the errorpage
+                // tree and not the one rendering the error page
                 ctx.getExternalContext().getRequestMap().put("com.sun.faces.error.view", ctx.getViewRoot());
             }
             throw fe;
diff --git a/impl/src/main/java/com/sun/faces/context/ExternalContextFactoryImpl.java b/impl/src/main/java/com/sun/faces/context/ExternalContextFactoryImpl.java
index 511b092984..d694c35c10 100644
--- a/impl/src/main/java/com/sun/faces/context/ExternalContextFactoryImpl.java
+++ b/impl/src/main/java/com/sun/faces/context/ExternalContextFactoryImpl.java
@@ -46,9 +46,7 @@ public ExternalContext getExternalContext(Object servletContext, Object request,
 
         ExternalContext extContext = new ExternalContextImpl((ServletContext) servletContext, (ServletRequest) request, (ServletResponse) response);
 
-        if (request instanceof ServletRequest) {
-            ((ServletRequest) request).setAttribute(DEFAULT_EXTERNAL_CONTEXT_KEY, extContext);
-        }
+        ((ServletRequest) request).setAttribute(DEFAULT_EXTERNAL_CONTEXT_KEY, extContext);
 
         return extContext;
 
diff --git a/impl/src/main/java/com/sun/faces/context/ExternalContextImpl.java b/impl/src/main/java/com/sun/faces/context/ExternalContextImpl.java
index 9e1ae9910b..8e6470166e 100644
--- a/impl/src/main/java/com/sun/faces/context/ExternalContextImpl.java
+++ b/impl/src/main/java/com/sun/faces/context/ExternalContextImpl.java
@@ -97,7 +97,7 @@ public class ExternalContextImpl extends ExternalContext {
     private Map<String, String> initParameterMap = null;
     private Map<String, String> fallbackContentTypeMap = null;
     private Flash flash;
-    private boolean distributable;
+    private final boolean distributable;
 
     private enum PREDEFINED_COOKIE_PROPERTIES {
         domain, maxAge, path, secure, httpOnly, attribute;
@@ -112,7 +112,7 @@ static PREDEFINED_COOKIE_PROPERTIES of(String key) {
         }
     }
 
-    static final Class theUnmodifiableMapClass = Collections.unmodifiableMap(new HashMap<>()).getClass();
+    static final Class<? extends Map> theUnmodifiableMapClass = Collections.unmodifiableMap(new HashMap<>()).getClass();
 
     // ------------------------------------------------------------ Constructors
 
@@ -130,15 +130,16 @@ public ExternalContextImpl(ServletContext sc, ServletRequest request, ServletRes
 
         boolean enabled = ContextParamUtils.getValue(servletContext, SendPoweredByHeader, Boolean.class);
         if (enabled) {
-            ((HttpServletResponse) response).addHeader("X-Powered-By", "Faces/3.0");
+            ((HttpServletResponse) response).addHeader("X-Powered-By", "Faces/4.0");
         }
 
         distributable = ContextParamUtils.getValue(servletContext, ContextParam.EnableDistributable, Boolean.class);
 
-        fallbackContentTypeMap = new HashMap<>(3, 1.0f);
-        fallbackContentTypeMap.put("js", ScriptRenderer.DEFAULT_CONTENT_TYPE);
-        fallbackContentTypeMap.put("css", StylesheetRenderer.DEFAULT_CONTENT_TYPE);
-        fallbackContentTypeMap.put("properties", "text/plain");
+        fallbackContentTypeMap = Map.of(
+                "js", ScriptRenderer.DEFAULT_CONTENT_TYPE,
+                "css", StylesheetRenderer.DEFAULT_CONTENT_TYPE,
+                "properties", "text/plain"
+        );
 
     }
 
@@ -154,10 +155,9 @@ public Object getSession(boolean create) {
 
     @Override
     public String getSessionId(boolean create) {
-        HttpSession session = null;
         String id = null;
 
-        session = (HttpSession) getSession(create);
+        HttpSession session = (HttpSession) getSession(create);
         if (session != null) {
             id = session.getId();
         }
@@ -198,7 +198,6 @@ public void setRequest(Object request) {
             this.request = (ServletRequest) request;
             requestHeaderMap = null;
             requestHeaderValuesMap = null;
-            requestHeaderValuesMap = null;
             requestMap = null;
             requestParameterMap = null;
             requestParameterValuesMap = null;
@@ -362,9 +361,9 @@ public Map<String, String[]> getRequestParameterValuesMap() {
      */
     @Override
     public Iterator<String> getRequestParameterNames() {
-        final Enumeration namEnum = request.getParameterNames();
+        final Enumeration<String> namEnum = request.getParameterNames();
 
-        return new Iterator<String>() {
+        return new Iterator<>() {
             @Override
             public boolean hasNext() {
                 return namEnum.hasMoreElements();
@@ -372,7 +371,7 @@ public boolean hasNext() {
 
             @Override
             public String next() {
-                return (String) namEnum.nextElement();
+                return namEnum.nextElement();
             }
 
             @Override
@@ -535,7 +534,7 @@ public String encodeActionURL(String url) {
         if (null != cw) {
             appendClientWindow = cw.isClientWindowRenderModeEnabled(context);
         }
-        if (appendClientWindow && -1 == url.indexOf(ResponseStateManager.CLIENT_WINDOW_URL_PARAM)) {
+        if (appendClientWindow && !url.contains(ResponseStateManager.CLIENT_WINDOW_URL_PARAM)) {
             if (null != cw) {
                 String clientWindowId = cw.getId();
                 StringBuilder builder = new StringBuilder(url);
@@ -1042,7 +1041,6 @@ public void release() {
         request = null;
         response = null;
         clientWindow = null;
-
         applicationMap = null;
         sessionMap = null;
         requestMap = null;
@@ -1126,11 +1124,11 @@ public String getFallbackMimeType(String file) {
 
     private static class LocalesIterator implements Iterator<Locale> {
 
-        public LocalesIterator(Enumeration locales) {
+        public LocalesIterator(Enumeration<Locale> locales) {
             this.locales = locales;
         }
 
-        private Enumeration locales;
+        private final Enumeration<Locale> locales;
 
         @Override
         public boolean hasNext() {
@@ -1139,7 +1137,7 @@ public boolean hasNext() {
 
         @Override
         public Locale next() {
-            return (Locale) locales.nextElement();
+            return locales.nextElement();
         }
 
         @Override
diff --git a/impl/src/main/java/com/sun/faces/context/FacesContextFactoryImpl.java b/impl/src/main/java/com/sun/faces/context/FacesContextFactoryImpl.java
index c4aff33cf5..2d65ad7b42 100644
--- a/impl/src/main/java/com/sun/faces/context/FacesContextFactoryImpl.java
+++ b/impl/src/main/java/com/sun/faces/context/FacesContextFactoryImpl.java
@@ -91,7 +91,7 @@ private void savePerRequestInitParams(FacesContext context, WebConfiguration web
                 webConfig.isOptionEnabled(ViewRootPhaseListenerQueuesException) ? Boolean.TRUE : Boolean.FALSE);
         attrs.put(EnableValidateWholeBean.getQualifiedName(), webConfig.isOptionEnabled(EnableValidateWholeBean) ? Boolean.TRUE : Boolean.FALSE);
 
-        String facesConfigVersion = "" + appMap.get(RIConstants.FACES_CONFIG_VERSION);
+        String facesConfigVersion = String.valueOf(appMap.get(RIConstants.FACES_CONFIG_VERSION));
         attrs.put(RIConstants.FACES_CONFIG_VERSION, facesConfigVersion);
     }
 
diff --git a/impl/src/main/java/com/sun/faces/context/InitParameterMap.java b/impl/src/main/java/com/sun/faces/context/InitParameterMap.java
index 860527d90f..7c41a21cd6 100644
--- a/impl/src/main/java/com/sun/faces/context/InitParameterMap.java
+++ b/impl/src/main/java/com/sun/faces/context/InitParameterMap.java
@@ -76,8 +76,8 @@ public boolean equals(Object obj) {
     @Override
     public int hashCode() {
         int hashCode = 7 * servletContext.hashCode();
-        for (Iterator i = entrySet().iterator(); i.hasNext();) {
-            hashCode += i.next().hashCode();
+        for (Map.Entry<String, String> stringStringEntry : entrySet()) {
+            hashCode += stringStringEntry.hashCode();
         }
         return hashCode;
     }
diff --git a/impl/src/main/java/com/sun/faces/context/PartialViewContextImpl.java b/impl/src/main/java/com/sun/faces/context/PartialViewContextImpl.java
index 2d650e03cf..961155f544 100644
--- a/impl/src/main/java/com/sun/faces/context/PartialViewContextImpl.java
+++ b/impl/src/main/java/com/sun/faces/context/PartialViewContextImpl.java
@@ -65,7 +65,7 @@
 public class PartialViewContextImpl extends PartialViewContext {
 
     // Log instance for this class
-    private static Logger LOGGER = FacesLogger.CONTEXT.getLogger();
+    private static final Logger LOGGER = FacesLogger.CONTEXT.getLogger();
 
     private boolean released;
 
diff --git a/impl/src/main/java/com/sun/faces/context/RequestCookieMap.java b/impl/src/main/java/com/sun/faces/context/RequestCookieMap.java
index b8ef82ec05..954688d1aa 100644
--- a/impl/src/main/java/com/sun/faces/context/RequestCookieMap.java
+++ b/impl/src/main/java/com/sun/faces/context/RequestCookieMap.java
@@ -56,9 +56,9 @@ public Object get(Object key) {
         String keyString = key.toString();
         Object result = null;
 
-        for (int i = 0; i < cookies.length; i++) {
-            if (cookies[i].getName().equals(keyString)) {
-                result = cookies[i];
+        for (Cookie cookie : cookies) {
+            if (cookie.getName().equals(keyString)) {
+                result = cookie;
                 break;
             }
         }
@@ -88,8 +88,8 @@ public boolean equals(Object obj) {
     @Override
     public int hashCode() {
         int hashCode = 7 * request.hashCode();
-        for (Iterator i = entrySet().iterator(); i.hasNext();) {
-            hashCode += i.next().hashCode();
+        for (Map.Entry<String, Object> stringObjectEntry : entrySet()) {
+            hashCode += stringObjectEntry.hashCode();
         }
         return hashCode;
     }
@@ -113,7 +113,7 @@ protected Iterator<Object> getValueIterator() {
 
     // ----------------------------------------------------------- Inner Classes
 
-    private static class CookieArrayEnumerator implements Enumeration {
+    private static class CookieArrayEnumerator implements Enumeration<String> {
 
         Cookie[] cookies;
         int curIndex = -1;
@@ -130,7 +130,7 @@ public boolean hasMoreElements() {
         }
 
         @Override
-        public Object nextElement() {
+        public String nextElement() {
             curIndex++;
             if (curIndex < upperBound) {
                 return cookies[curIndex].getName();
diff --git a/impl/src/main/java/com/sun/faces/context/RequestHeaderMap.java b/impl/src/main/java/com/sun/faces/context/RequestHeaderMap.java
index 14c2b2aa79..7173c9da14 100644
--- a/impl/src/main/java/com/sun/faces/context/RequestHeaderMap.java
+++ b/impl/src/main/java/com/sun/faces/context/RequestHeaderMap.java
@@ -76,8 +76,8 @@ public boolean equals(Object obj) {
     @Override
     public int hashCode() {
         int hashCode = 7 * request.hashCode();
-        for (Iterator i = entrySet().iterator(); i.hasNext();) {
-            hashCode += i.next().hashCode();
+        for (Map.Entry<String, String> stringStringEntry : entrySet()) {
+            hashCode += stringStringEntry.hashCode();
         }
         return hashCode;
     }
diff --git a/impl/src/main/java/com/sun/faces/context/RequestHeaderValuesMap.java b/impl/src/main/java/com/sun/faces/context/RequestHeaderValuesMap.java
index 99013b46ed..d345d12f35 100644
--- a/impl/src/main/java/com/sun/faces/context/RequestHeaderValuesMap.java
+++ b/impl/src/main/java/com/sun/faces/context/RequestHeaderValuesMap.java
@@ -54,12 +54,12 @@ public String[] get(Object key) {
         Util.notNull("key", key);
 
         List<String> valuesList = new ArrayList<>();
-        Enumeration valuesEnum = request.getHeaders(key.toString());
+        Enumeration<String> valuesEnum = request.getHeaders(key.toString());
         while (valuesEnum.hasMoreElements()) {
-            valuesList.add((String) valuesEnum.nextElement());
+            valuesList.add(valuesEnum.nextElement());
         }
 
-        return valuesList.toArray(new String[valuesList.size()]);
+        return valuesList.toArray(new String[0]);
     }
 
     @Override
diff --git a/impl/src/main/java/com/sun/faces/context/RequestMap.java b/impl/src/main/java/com/sun/faces/context/RequestMap.java
index 9a91d96091..59c49eff35 100644
--- a/impl/src/main/java/com/sun/faces/context/RequestMap.java
+++ b/impl/src/main/java/com/sun/faces/context/RequestMap.java
@@ -48,7 +48,7 @@ public void clear() {
 
     // Supported by maps if overridden
     @Override
-    public void putAll(Map t) {
+    public void putAll(Map<? extends String, ?> t) {
         for (Iterator i = t.entrySet().iterator(); i.hasNext();) {
             Map.Entry entry = (Map.Entry) i.next();
             request.setAttribute((String) entry.getKey(), entry.getValue());
diff --git a/impl/src/main/java/com/sun/faces/context/RequestParameterMap.java b/impl/src/main/java/com/sun/faces/context/RequestParameterMap.java
index 309a10cc94..402c696830 100644
--- a/impl/src/main/java/com/sun/faces/context/RequestParameterMap.java
+++ b/impl/src/main/java/com/sun/faces/context/RequestParameterMap.java
@@ -54,7 +54,7 @@ public String get(Object key) {
         String mapKey = key.toString();
         String mapValue = request.getParameter(mapKey);
         if (mapValue == null && !mapKey.startsWith(getNamingContainerPrefix())) {
-            // Support cases where enduser manually obtains a request parameter while in a namespaced view.
+            // Support cases where end user manually obtains a request parameter while in a namespaced view.
             mapValue = request.getParameter(getNamingContainerPrefix() + mapKey);
         }
         return mapValue;
@@ -107,8 +107,8 @@ public boolean equals(Object obj) {
     @Override
     public int hashCode() {
         int hashCode = 7 * request.hashCode();
-        for (Iterator i = entrySet().iterator(); i.hasNext();) {
-            hashCode += i.next().hashCode();
+        for (Map.Entry<String, String> stringStringEntry : entrySet()) {
+            hashCode += stringStringEntry.hashCode();
         }
         return hashCode;
     }
diff --git a/impl/src/main/java/com/sun/faces/context/SessionMap.java b/impl/src/main/java/com/sun/faces/context/SessionMap.java
index 9ccf3b3c8b..eb23164d3b 100644
--- a/impl/src/main/java/com/sun/faces/context/SessionMap.java
+++ b/impl/src/main/java/com/sun/faces/context/SessionMap.java
@@ -17,10 +17,7 @@
 package com.sun.faces.context;
 
 import java.io.Serializable;
-import java.util.Collections;
-import java.util.Enumeration;
-import java.util.Iterator;
-import java.util.Map;
+import java.util.*;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -54,8 +51,8 @@ public SessionMap(HttpServletRequest request, ProjectStage stage) {
     public void clear() {
         HttpSession session = getSession(false);
         if (session != null) {
-            for (Enumeration e = session.getAttributeNames(); e.hasMoreElements();) {
-                String name = (String) e.nextElement();
+            for (Enumeration<String> e = session.getAttributeNames(); e.hasMoreElements();) {
+                String name = e.nextElement();
                 session.removeAttribute(name);
             }
         }
@@ -63,20 +60,17 @@ public void clear() {
 
     // Supported by maps if overridden
     @Override
-    public void putAll(Map t) {
+    public void putAll(Map<? extends String, ?> map) {
         HttpSession session = getSession(true);
-        for (Iterator i = t.entrySet().iterator(); i.hasNext();) {
-            Map.Entry entry = (Map.Entry) i.next();
-            Object v = entry.getValue();
-            Object k = entry.getKey();
-            if (ProjectStage.Development.equals(stage) && !(v instanceof Serializable)) {
+        map.forEach( (key, value) -> {
+            if (ProjectStage.Development.equals(stage) && !(value instanceof Serializable)) {
                 if (LOGGER.isLoggable(Level.WARNING)) {
-                    LOGGER.log(Level.WARNING, "faces.context.extcontext.sessionmap.nonserializable", new Object[] { k, v.getClass().getName() });
+                    LOGGER.log(Level.WARNING, "faces.context.extcontext.sessionmap.nonserializable", new Object[]{key, value.getClass().getName()});
                 }
             }
             // noinspection NonSerializableObjectBoundToHttpSession
-            session.setAttribute((String) k, v);
-        }
+            session.setAttribute(key, value);
+        });
     }
 
     @Override
@@ -133,7 +127,7 @@ public boolean containsKey(Object key) {
 
     @Override
     public boolean equals(Object obj) {
-        return !(obj == null || !(obj instanceof SessionMap)) && super.equals(obj);
+        return obj instanceof SessionMap && super.equals(obj);
     }
 
     @Override
@@ -141,8 +135,8 @@ public int hashCode() {
         HttpSession session = getSession(false);
         int hashCode = 7 * (session != null ? session.hashCode() : super.hashCode());
         if (session != null) {
-            for (Iterator i = entrySet().iterator(); i.hasNext();) {
-                hashCode += i.next().hashCode();
+            for (Map.Entry<String,Object> stringObjectEntry : entrySet()) {
+                hashCode += stringObjectEntry.hashCode();
             }
         }
         return hashCode;
@@ -156,8 +150,7 @@ protected Iterator<Map.Entry<String, Object>> getEntryIterator() {
         if (session != null) {
             return new EntryIterator(session.getAttributeNames());
         } else {
-            Map<String, Object> empty = Collections.emptyMap();
-            return empty.entrySet().iterator();
+            return Collections.emptyIterator();
         }
     }
 
@@ -167,8 +160,7 @@ protected Iterator<String> getKeyIterator() {
         if (session != null) {
             return new KeyIterator(session.getAttributeNames());
         } else {
-            Map<String, Object> empty = Collections.emptyMap();
-            return empty.keySet().iterator();
+            return Collections.emptyIterator();
         }
     }
 
@@ -178,8 +170,7 @@ protected Iterator<Object> getValueIterator() {
         if (session != null) {
             return new ValueIterator(session.getAttributeNames());
         } else {
-            Map<String, Object> empty = Collections.emptyMap();
-            return empty.values().iterator();
+            return Collections.emptyIterator();
         }
     }
 
diff --git a/impl/src/main/java/com/sun/faces/context/StateContext.java b/impl/src/main/java/com/sun/faces/context/StateContext.java
index 32811c7164..8c0d3af7d1 100644
--- a/impl/src/main/java/com/sun/faces/context/StateContext.java
+++ b/impl/src/main/java/com/sun/faces/context/StateContext.java
@@ -63,7 +63,7 @@ public class StateContext {
     private boolean partialLocked;
     private boolean trackMods = true;
     private AddRemoveListener modListener;
-    private ApplicationStateInfo stateInfo;
+    private final ApplicationStateInfo stateInfo;
     private WeakReference<UIViewRoot> viewRootRef = new WeakReference<>(null);
 
     private static final Logger LOGGER = FacesLogger.CONTEXT.getLogger();
@@ -252,7 +252,7 @@ public List<ComponentStruct> getDynamicActions() {
      *
      * @return the hash map of dynamic components.
      */
-    public HashMap<String, UIComponent> getDynamicComponents() {
+    public Map<String, UIComponent> getDynamicComponents() {
         return modListener != null ? modListener.getDynamicComponents() : null;
     }
 
@@ -262,12 +262,12 @@ private AddRemoveListener createAddRemoveListener(FacesContext context, UIViewRo
         return isPartialStateSaving(context, root.getViewId()) ? new DynamicAddRemoveListener(context) : new StatelessAddRemoveListener(context);
     }
 
-    abstract private class AddRemoveListener implements SystemEventListener {
+    abstract private static class AddRemoveListener implements SystemEventListener {
 
         /**
          * Stores the state context we work for,
          */
-        private StateContext stateCtx;
+        private final StateContext stateCtx;
 
         /**
          * Constructor.
@@ -290,7 +290,7 @@ protected AddRemoveListener(FacesContext context) {
          *
          * @return the hash map of dynamic components.
          */
-        abstract public HashMap<String, UIComponent> getDynamicComponents();
+        abstract public Map<String, UIComponent> getDynamicComponents();
 
         /**
          * Process the add/remove event.
@@ -346,12 +346,12 @@ public boolean isListenerForSource(Object source) {
         abstract protected void handleAdd(FacesContext context, UIComponent component);
     }
 
-    public class NoopAddRemoveListener extends AddRemoveListener {
+    public static class NoopAddRemoveListener extends AddRemoveListener {
 
-        // This is silly. We should be able to use Colletions.emptyMap(),
+        // This is silly. We should be able to use Collections.emptyMap(),
         // but cannot as StateContext.getDynamicComponents() API returns a
         // HashMap instead of a Map.
-        private HashMap emptyComponentsMap = new HashMap();
+        private final Map<String, UIComponent> emptyComponentsMap = Collections.emptyMap();
 
         public NoopAddRemoveListener(FacesContext context) {
             super(context);
@@ -363,7 +363,7 @@ public List<ComponentStruct> getDynamicActions() {
         }
 
         @Override
-        public HashMap<String, UIComponent> getDynamicComponents() {
+        public Map<String, UIComponent> getDynamicComponents() {
             return emptyComponentsMap;
         }
 
@@ -381,7 +381,7 @@ protected void handleAdd(FacesContext context, UIComponent component) {
      * itself. Instead, we use expando attributes on the dynamic components (and their parents) to track/preserve the
      * dynamic nature of these components.
      */
-    public class StatelessAddRemoveListener extends NoopAddRemoveListener {
+    public static class StatelessAddRemoveListener extends NoopAddRemoveListener {
 
         public StatelessAddRemoveListener(FacesContext context) {
             super(context);
@@ -564,7 +564,7 @@ public List<ComponentStruct> getDynamicActions() {
          * @return the hash map of dynamic components.
          */
         @Override
-        public HashMap<String, UIComponent> getDynamicComponents() {
+        public Map<String, UIComponent> getDynamicComponents() {
             synchronized (this) {
                 if (dynamicComponents == null) {
                     dynamicComponents = new HashMap<>();
@@ -639,16 +639,13 @@ protected void handleAdd(FacesContext context, UIComponent component) {
          * @param component the component to look for in the facets map entry value.
          * @return the facet name or null if the component is not the value of a facets map entry.
          */
-        private String findFacetNameForComponent(UIComponent component) {
+        private String findFacetNameForComponent(final UIComponent component) {
             Set<Entry<String, UIComponent>> entrySet = component.getParent().getFacets().entrySet();
-            Iterator<Entry<String, UIComponent>> entries = entrySet.iterator();
-            while (entries.hasNext()) {
-                Entry<String, UIComponent> candidate = entries.next();
-                if (component == candidate.getValue()) {
-                    return candidate.getKey();
-                }
-            }
-            return null;
+            return entrySet.stream()
+                           .filter(candidate -> component.equals(candidate.getValue()))
+                           .findFirst()
+                           .map(Entry::getKey)
+                           .orElse(null);
         }
 
         /**
@@ -686,7 +683,7 @@ private String findFacetNameForComponent(UIComponent component) {
          */
         private void handleAddRemoveWithAutoPrune(UIComponent component, ComponentStruct struct) {
             List<ComponentStruct> actionList = getDynamicActions();
-            HashMap<String, UIComponent> componentMap = getDynamicComponents();
+            Map<String, UIComponent> componentMap = getDynamicComponents();
 
             int firstIndex = actionList.indexOf(struct);
             if (firstIndex == -1) {
diff --git a/impl/src/main/java/com/sun/faces/context/StateHolderSaver.java b/impl/src/main/java/com/sun/faces/context/StateHolderSaver.java
index 712cbbe4ef..4cb359c65d 100644
--- a/impl/src/main/java/com/sun/faces/context/StateHolderSaver.java
+++ b/impl/src/main/java/com/sun/faces/context/StateHolderSaver.java
@@ -17,6 +17,7 @@
 package com.sun.faces.context;
 
 import java.io.Serializable;
+import java.lang.reflect.InvocationTargetException;
 
 import jakarta.faces.component.StateHolder;
 import jakarta.faces.component.UIComponent;
@@ -124,17 +125,13 @@ public Object restore(FacesContext context) throws IllegalStateException {
             throw new IllegalStateException(e);
         }
 
-        if (null != toRestoreClass) {
-            try {
-                result = toRestoreClass.newInstance();
-            } catch (InstantiationException e) {
-                throw new IllegalStateException(e);
-            } catch (IllegalAccessException a) {
-                throw new IllegalStateException(a);
-            }
+        try {
+            result = toRestoreClass.getDeclaredConstructor().newInstance();
+        } catch (InstantiationException | IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
+            throw new IllegalStateException(e);
         }
 
-        if (null != result && null != savedState && result instanceof StateHolder) {
+        if (null != savedState && result instanceof StateHolder) {
             // don't need to check transient, since that was done on
             // the saving side.
             Serializable[] tuple = (Serializable[]) savedState;
@@ -143,7 +140,7 @@ public Object restore(FacesContext context) throws IllegalStateException {
         return result;
     }
 
-    private static Class loadClass(String name, Object fallbackClass) throws ClassNotFoundException {
+    private static Class<?> loadClass(String name, Object fallbackClass) throws ClassNotFoundException {
         ClassLoader loader = Thread.currentThread().getContextClassLoader();
         if (loader == null) {
             loader = fallbackClass.getClass().getClassLoader();
diff --git a/impl/src/main/java/com/sun/faces/context/StringArrayValuesMap.java b/impl/src/main/java/com/sun/faces/context/StringArrayValuesMap.java
index 07293ff87d..8e7104d84b 100644
--- a/impl/src/main/java/com/sun/faces/context/StringArrayValuesMap.java
+++ b/impl/src/main/java/com/sun/faces/context/StringArrayValuesMap.java
@@ -18,6 +18,7 @@
 
 import java.util.Arrays;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 
 /**
@@ -36,15 +37,12 @@ public boolean containsValue(Object value) {
             return false;
         }
 
-        Set entrySet = entrySet();
-        for (Object anEntrySet : entrySet) {
-            Map.Entry entry = (Map.Entry) anEntrySet;
-            // values will be arrays
-            if (Arrays.equals((Object[]) value, (Object[]) entry.getValue())) {
-                return true;
-            }
-        }
-        return false;
+        final Object[] array = (Object[]) value;
+
+        // values will be arrays
+        return entrySet().stream()
+                         .map(Map.Entry::getValue)
+                         .anyMatch(v -> Arrays.equals(array, v));
     }
 
     @Override
@@ -89,10 +87,9 @@ public int hashCode() {
 
     protected int hashCode(Object someObject) {
         int hashCode = 7 * someObject.hashCode();
-        for (Object o : entrySet()) {
-            Map.Entry entry = (Map.Entry) o;
+        for ( Map.Entry<String,String[]> entry : entrySet()) {
             hashCode += entry.getKey().hashCode();
-            hashCode += Arrays.hashCode((Object[]) entry.getValue());
+            hashCode += Arrays.hashCode(entry.getValue());
         }
         return hashCode;
     }
diff --git a/impl/src/main/java/com/sun/faces/context/UrlBuilder.java b/impl/src/main/java/com/sun/faces/context/UrlBuilder.java
index d51c3fb83d..c040a3f17e 100644
--- a/impl/src/main/java/com/sun/faces/context/UrlBuilder.java
+++ b/impl/src/main/java/com/sun/faces/context/UrlBuilder.java
@@ -16,21 +16,15 @@
 
 package com.sun.faces.context;
 
-import java.io.UnsupportedEncodingException;
-import java.net.URLEncoder;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Iterator;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-
 import com.sun.faces.util.Util;
-
 import jakarta.faces.context.FacesContext;
 import jakarta.faces.lifecycle.ClientWindow;
 import jakarta.faces.render.ResponseStateManager;
 
+import java.net.URLEncoder;
+import java.nio.charset.Charset;
+import java.util.*;
+
 /**
  * <p>
  * The <strong>UrlBuilder</strong> provides a convenient way to assemble a URL. It follows the standard Builder Pattern.
@@ -51,14 +45,14 @@ class UrlBuilder {
     public static final String FRAGMENT_SEPARATOR = "#";
     public static final String DEFAULT_ENCODING = "UTF-8";
 
-    private static final List<String> NULL_LIST = Arrays.asList((String) null);
+    private static final List<String> NULL_LIST = Collections.singletonList(null);
 
-    private StringBuilder url;
+    private final StringBuilder url;
     private String path;
     private String queryString;
     private String fragment;
     private Map<String, List<String>> parameters;
-    private String encoding;
+    private final Charset encoding;
 
     // ------------------------------------------------------------ Constructors
 
@@ -68,7 +62,7 @@ public UrlBuilder(String url, String encoding) {
         }
         this.url = new StringBuilder(url.length() * 2);
         extractSegments(url);
-        this.encoding = encoding;
+        this.encoding = Charset.forName(encoding);
         // PERF TL lookup per-instance
     }
 
@@ -93,8 +87,7 @@ public UrlBuilder addParameters(Map<String, List<String>> params) {
                 if (entry.getKey() == null || entry.getKey().trim().length() == 0) {
                     throw new IllegalArgumentException("Parameter name cannot be empty");
                 }
-                List<String> values = entry.getValue();
-                List<String> retValues = values;
+                List<String> retValues = entry.getValue();
                 addValuesToParameter(entry.getKey().trim(), retValues, true);
             }
         }
@@ -268,14 +261,9 @@ protected void addValueToParameter(String name, String value, boolean replace) {
     protected void addValuesToParameter(String name, List<String> valuesRef, boolean replace) {
         List<String> values = new ArrayList<>();
         if (valuesRef != null) {
-            for (Iterator<String> it = valuesRef.iterator(); it.hasNext();) {
-                String string = it.next();
+            for (String string : valuesRef) {
                 if (encoding != null) {
-                    try {
-                        values.add(URLEncoder.encode(string, encoding));
-                    } catch (UnsupportedEncodingException ex) {
-                        throw new RuntimeException(ex);
-                    }
+                    values.add(URLEncoder.encode(string, encoding));
                 } else {
                     values.add(string);
                 }
@@ -290,12 +278,7 @@ protected void addValuesToParameter(String name, List<String> valuesRef, boolean
         if (replace) {
             parameters.put(name, values);
         } else {
-            List<String> currentValues = parameters.get(name);
-            if (currentValues == null) {
-                currentValues = new ArrayList<>(1);
-                parameters.put(name, currentValues);
-            }
-            currentValues.addAll(values);
+            parameters.computeIfAbsent(name, k -> new ArrayList<>(1)).addAll(values);
         }
     }
 
diff --git a/impl/src/main/java/com/sun/faces/el/CompositeComponentAttributesELResolver.java b/impl/src/main/java/com/sun/faces/el/CompositeComponentAttributesELResolver.java
index 6609db3803..be23afbd9c 100644
--- a/impl/src/main/java/com/sun/faces/el/CompositeComponentAttributesELResolver.java
+++ b/impl/src/main/java/com/sun/faces/el/CompositeComponentAttributesELResolver.java
@@ -296,8 +296,8 @@ private static final class ExpressionEvalMap implements Map<String, Object>, Com
 
         @Override
         public ValueExpression getExpression(String name) {
-            Object ve = cc.getValueExpression(name);
-            return ve instanceof ValueExpression ? (ValueExpression) ve : null;
+            return cc.getValueExpression(name);
+//            return ve instanceof ValueExpression ? (ValueExpression) ve : null;
         }
 
         // ---------------------------------------------------- Methods from Map
@@ -335,15 +335,12 @@ public Object get(Object key) {
                     return ((ValueExpression) v).getValue(ctx.getELContext());
                 }
             }
-            if (v != null && v instanceof MethodExpression) {
-                return v;
-            }
             return v;
         }
 
         @Override
         public Object put(String key, Object value) {
-            // Unlinke AttributesMap.get() which will obtain a value from
+            // Unlike AttributesMap.get() which will obtain a value from
             // a ValueExpression, AttributesMap.put(), when passed a value,
             // will never call ValueExpression.setValue(), so we have to take
             // matters into our own hands...
diff --git a/impl/src/main/java/com/sun/faces/el/ELContextImpl.java b/impl/src/main/java/com/sun/faces/el/ELContextImpl.java
index 723c75b779..0061038cba 100644
--- a/impl/src/main/java/com/sun/faces/el/ELContextImpl.java
+++ b/impl/src/main/java/com/sun/faces/el/ELContextImpl.java
@@ -43,7 +43,7 @@ public class ELContextImpl extends ELContext {
 
     private FunctionMapper functionMapper = new NoopFunctionMapper();
     private VariableMapper variableMapper;
-    private ELResolver resolver;
+    private final ELResolver resolver;
 
     // ------------------------------------------------------------ Constructors
 
@@ -66,7 +66,7 @@ public ELContextImpl(FacesContext facesContext) {
             putContext(ExpressionFactory.class, expressionFactory);
         }
 
-        if (facesContext instanceof InitFacesContext == false) {
+        if ( !(facesContext instanceof InitFacesContext) ) {
             UIViewRoot root = facesContext.getViewRoot();
             if (root != null) {
                 setLocale(root.getLocale());
@@ -104,7 +104,7 @@ public void setFunctionMapper(FunctionMapper functionMapper) {
 
     private static class VariableMapperImpl extends VariableMapper {
 
-        private Map<String, ValueExpression> variables;
+        private final Map<String, ValueExpression> variables;
 
         public VariableMapperImpl() {
             variables = new HashMap<>();
diff --git a/impl/src/main/java/com/sun/faces/el/ELContextListenerImpl.java b/impl/src/main/java/com/sun/faces/el/ELContextListenerImpl.java
index cec107e9b6..bd210c956a 100644
--- a/impl/src/main/java/com/sun/faces/el/ELContextListenerImpl.java
+++ b/impl/src/main/java/com/sun/faces/el/ELContextListenerImpl.java
@@ -53,8 +53,7 @@ public void contextCreated(ELContextEvent ece) {
         if (listeners == null) {
             return;
         }
-        for (int i = 0; i < listeners.length; ++i) {
-            ELContextListener elcl = listeners[i];
+        for (ELContextListener elcl : listeners) {
             elcl.contextCreated(new ELContextEvent(source));
         }
     }
diff --git a/impl/src/main/java/com/sun/faces/el/ELUtils.java b/impl/src/main/java/com/sun/faces/el/ELUtils.java
index dee44542e7..3fa323bb79 100644
--- a/impl/src/main/java/com/sun/faces/el/ELUtils.java
+++ b/impl/src/main/java/com/sun/faces/el/ELUtils.java
@@ -128,7 +128,7 @@ public static boolean isCompositeComponentExpr(String expression) {
 
         if (evaluationResult != null) {
             // fast path - this expression has already been evaluated, therefore return its evaluation result
-            return evaluationResult.booleanValue();
+            return evaluationResult;
         }
 
         // TODO we should be trying to re-use the Matcher by calling
diff --git a/impl/src/main/java/com/sun/faces/el/FacesResourceBundleELResolver.java b/impl/src/main/java/com/sun/faces/el/FacesResourceBundleELResolver.java
index b87b00bbcc..147555ea8c 100644
--- a/impl/src/main/java/com/sun/faces/el/FacesResourceBundleELResolver.java
+++ b/impl/src/main/java/com/sun/faces/el/FacesResourceBundleELResolver.java
@@ -17,11 +17,7 @@
 package com.sun.faces.el;
 
 import java.beans.FeatureDescriptor;
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.Locale;
-import java.util.Map;
-import java.util.ResourceBundle;
+import java.util.*;
 
 import com.sun.faces.application.ApplicationAssociate;
 import com.sun.faces.application.ApplicationResourceBundle;
@@ -140,17 +136,17 @@ public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Obje
             return null;
         }
 
-        ArrayList<FeatureDescriptor> list = new ArrayList<>();
+
 
         FacesContext facesContext = (FacesContext) context.getContext(FacesContext.class);
         ApplicationAssociate associate = ApplicationAssociate.getCurrentInstance();
         Map<String, ApplicationResourceBundle> rbMap = associate.getResourceBundles();
         if (rbMap == null) {
-            return list.iterator();
+            return Collections.emptyIterator();
         }
         // iterate over the list of managed beans
-        for (Iterator<Map.Entry<String, ApplicationResourceBundle>> i = rbMap.entrySet().iterator(); i.hasNext();) {
-            Map.Entry<String, ApplicationResourceBundle> entry = i.next();
+        List<FeatureDescriptor> list = new ArrayList<>();
+        for (Map.Entry<String, ApplicationResourceBundle> entry : rbMap.entrySet()) {
             String var = entry.getKey();
             ApplicationResourceBundle bundle = entry.getValue();
             if (bundle != null) {
diff --git a/impl/src/main/java/com/sun/faces/el/ScopedAttributeELResolver.java b/impl/src/main/java/com/sun/faces/el/ScopedAttributeELResolver.java
index 83ff7a0d8c..3225b1101a 100644
--- a/impl/src/main/java/com/sun/faces/el/ScopedAttributeELResolver.java
+++ b/impl/src/main/java/com/sun/faces/el/ScopedAttributeELResolver.java
@@ -83,11 +83,7 @@ public Object getValue(ELContext elContext, Object base, Object property) throws
 
         // check application
         result = externalContext.getApplicationMap().get(attribute);
-        if (result != null) {
-            return result;
-        }
-
-        return null;
+        return result;
     }
 
     @Override
diff --git a/impl/src/main/java/com/sun/faces/ext/component/MessageFactory.java b/impl/src/main/java/com/sun/faces/ext/component/MessageFactory.java
index 14f5b20b8d..e6d6d71023 100644
--- a/impl/src/main/java/com/sun/faces/ext/component/MessageFactory.java
+++ b/impl/src/main/java/com/sun/faces/ext/component/MessageFactory.java
@@ -183,7 +183,7 @@ private static Application getApplication() {
         return afactory.getApplication();
     }
 
-    private static ClassLoader getCurrentLoader(Class fallbackClass) {
+    private static ClassLoader getCurrentLoader(Class<?> fallbackClass) {
         ClassLoader loader = Thread.currentThread().getContextClassLoader();
         if (loader == null) {
             loader = fallbackClass.getClassLoader();
@@ -255,7 +255,7 @@ private String getFormattedString(String msgtext, Object[] params) {
             if (params == null || msgtext == null) {
                 return msgtext;
             }
-            StringBuffer b = new StringBuffer(100);
+            StringBuilder b = new StringBuilder(100);
             MessageFormat mf = new MessageFormat(msgtext);
             if (locale != null) {
                 mf.setLocale(locale);
@@ -265,8 +265,8 @@ private String getFormattedString(String msgtext, Object[] params) {
             return localizedStr;
         }
 
-        private Locale locale;
-        private Object[] parameters;
+        private final Locale locale;
+        private final Object[] parameters;
         private Object[] resolvedParameters;
     }
 
diff --git a/impl/src/main/java/com/sun/faces/ext/component/UIValidateWholeBean.java b/impl/src/main/java/com/sun/faces/ext/component/UIValidateWholeBean.java
index 10238200ad..e33300e7ea 100644
--- a/impl/src/main/java/com/sun/faces/ext/component/UIValidateWholeBean.java
+++ b/impl/src/main/java/com/sun/faces/ext/component/UIValidateWholeBean.java
@@ -66,7 +66,7 @@ public Object getSubmittedValue() {
     }
 
     @Override
-    public void setConverter(Converter converter) {
+    public void setConverter(Converter<?> converter) {
     }
 
     @Override
diff --git a/impl/src/main/java/com/sun/faces/facelets/compiler/CompilationManager.java b/impl/src/main/java/com/sun/faces/facelets/compiler/CompilationManager.java
index 2360230daa..c59fa4c3c4 100644
--- a/impl/src/main/java/com/sun/faces/facelets/compiler/CompilationManager.java
+++ b/impl/src/main/java/com/sun/faces/facelets/compiler/CompilationManager.java
@@ -446,9 +446,9 @@ private Tag trimJSFCAttribute(Tag tag) {
             TagAttribute[] oa = tag.getAttributes().getAll();
             TagAttribute[] na = new TagAttribute[oa.length - 1];
             int p = 0;
-            for (int i = 0; i < oa.length; i++) {
-                if (!"jsfc".equals(oa[i].getLocalName())) {
-                    na[p++] = oa[i];
+            for (TagAttribute tagAttribute : oa) {
+                if (!"jsfc".equals(tagAttribute.getLocalName())) {
+                    na[p++] = tagAttribute;
                 }
             }
             return new Tag(tag, new TagAttributesImpl(na));
@@ -479,7 +479,7 @@ private Tag trimNSAttributes(Tag tag) {
                 }
                 attrList.add(attr[i]);
             }
-            attr = attrList.toArray(new TagAttribute[attrList.size()]);
+            attr = attrList.toArray(new TagAttribute[0]);
             return new Tag(tag.getLocation(), tag.getNamespace(), tag.getLocalName(), tag.getQName(), new TagAttributesImpl(attr));
         }
     }
@@ -497,7 +497,7 @@ private CompilationUnit getViewRootUnitFromStack(Stack<CompilationUnit> units) {
             if (compilationUnit instanceof TagUnit) {
                 TagUnit tagUnit = (TagUnit) compilationUnit;
                 String ns = tagUnit.getTag().getNamespace();
-                if (CoreLibrary.NAMESPACES.contains(ns) && tagUnit.getTag().getLocalName().equals("view")) {
+                if (CoreLibrary.NAMESPACES.contains(ns) && "view".equals(tagUnit.getTag().getLocalName())) {
                     result = tagUnit;
                     break;
                 }
diff --git a/impl/src/main/java/com/sun/faces/facelets/compiler/SAXCompiler.java b/impl/src/main/java/com/sun/faces/facelets/compiler/SAXCompiler.java
index 4780104665..b945643662 100644
--- a/impl/src/main/java/com/sun/faces/facelets/compiler/SAXCompiler.java
+++ b/impl/src/main/java/com/sun/faces/facelets/compiler/SAXCompiler.java
@@ -251,9 +251,7 @@ public void processingInstruction(String target, String data) throws SAXExceptio
                 boolean processAsXhtml = unit.getWebConfiguration().getFaceletsConfiguration().isProcessCurrentDocumentAsFaceletsXhtml(alias);
 
                 if (processAsXhtml) {
-                    StringBuffer sb = new StringBuffer(64);
-                    sb.append("<?").append(target).append(' ').append(data).append("?>\n");
-                    unit.writeInstruction(sb.toString());
+                    unit.writeInstruction("<?" + target + ' ' + data + "?>\n");
                 }
             }
         }
@@ -391,7 +389,7 @@ public FaceletHandler doMetadataCompile(URL src, String alias) throws IOExceptio
         return doCompile(mgr, handler, src, alias);
     }
 
-    protected FaceletHandler doCompile(CompilationManager mngr, CompilationHandler handler, URL src, String alias) throws IOException {
+    private FaceletHandler doCompile(CompilationManager mngr, CompilationHandler handler, URL src, String alias) throws IOException {
 
         String encoding = getEncoding();
         try (InputStream is = new BufferedInputStream(src.openStream(), 1024);) {
@@ -426,7 +424,7 @@ private String getEncoding() {
         return result;
     }
 
-    protected static void writeXmlDecl(InputStream is, String encoding, CompilationManager mngr) throws IOException {
+    private static void writeXmlDecl(InputStream is, String encoding, CompilationManager mngr) throws IOException {
         is.mark(128);
         try {
             byte[] b = new byte[128];
diff --git a/impl/src/main/java/com/sun/faces/facelets/compiler/UILeaf.java b/impl/src/main/java/com/sun/faces/facelets/compiler/UILeaf.java
index c3a11263f2..349f84c177 100644
--- a/impl/src/main/java/com/sun/faces/facelets/compiler/UILeaf.java
+++ b/impl/src/main/java/com/sun/faces/facelets/compiler/UILeaf.java
@@ -164,7 +164,7 @@ protected void addFacesListener(FacesListener faces) {
     }
 
     @Override
-    protected FacesListener[] getFacesListeners(Class faces) {
+    protected FacesListener[] getFacesListeners(Class<?> faces) {
         return null;
     }
 
@@ -199,7 +199,7 @@ protected FacesContext getFacesContext() {
     }
 
     @Override
-    protected Renderer getRenderer(FacesContext faces) {
+    protected Renderer<? extends UIComponent> getRenderer(FacesContext faces) {
         return null;
     }
 
diff --git a/impl/src/main/java/com/sun/faces/facelets/component/UIRepeat.java b/impl/src/main/java/com/sun/faces/facelets/component/UIRepeat.java
index 217d790f7a..83132e0666 100644
--- a/impl/src/main/java/com/sun/faces/facelets/component/UIRepeat.java
+++ b/impl/src/main/java/com/sun/faces/facelets/component/UIRepeat.java
@@ -65,12 +65,12 @@ public class UIRepeat extends UINamingContainer {
 
     public static final String COMPONENT_FAMILY = "facelets";
 
-    private final static DataModel EMPTY_MODEL = new ListDataModel<>(Collections.emptyList());
+    private final static DataModel<?> EMPTY_MODEL = new ListDataModel<>(Collections.emptyList());
 
     // our data
     private Object value;
 
-    private transient DataModel model;
+    private transient DataModel<?> model;
 
     // variables
     private String var;
@@ -203,12 +203,12 @@ private void resetDataModel(FacesContext context) {
         }
     }
 
-    private void setDataModel(DataModel model) {
+    private void setDataModel(DataModel<?> model) {
         // noinspection unchecked
         this.model = model;
     }
 
-    private DataModel getDataModel() {
+    private DataModel<?> getDataModel() {
         if (model == null) {
             Object val = getValue();
             if (val == null) {
@@ -378,9 +378,9 @@ private void removeChildState(FacesContext faces, UIComponent c) {
         String id = c.getId();
         c.setId(id);
 
-        Iterator itr = c.getFacetsAndChildren();
+        Iterator<UIComponent> itr = c.getFacetsAndChildren();
         while (itr.hasNext()) {
-            removeChildState(faces, (UIComponent) itr.next());
+            removeChildState(faces, itr.next());
         }
         if (childState != null) {
             childState.remove(c.getClientId(faces));
@@ -400,9 +400,9 @@ private void saveChildState(FacesContext faces, UIComponent c) {
         }
 
         // continue hack
-        Iterator itr = c.getFacetsAndChildren();
+        Iterator<UIComponent> itr = c.getFacetsAndChildren();
         while (itr.hasNext()) {
-            saveChildState(faces, (UIComponent) itr.next());
+            saveChildState(faces, itr.next());
         }
     }
 
@@ -433,9 +433,9 @@ private void restoreChildState(FacesContext faces, UIComponent c) {
         }
 
         // continue hack
-        Iterator itr = c.getFacetsAndChildren();
+        Iterator<UIComponent> itr = c.getFacetsAndChildren();
         while (itr.hasNext()) {
-            restoreChildState(faces, (UIComponent) itr.next());
+            restoreChildState(faces, itr.next());
         }
     }
 
@@ -454,7 +454,7 @@ private boolean hasErrorMessages(FacesContext context) {
 
     private void setIndex(FacesContext ctx, int index) {
 
-        DataModel localModel = getDataModel();
+        DataModel<?> localModel = getDataModel();
 
         // save child state
         if (this.index != -1 && localModel.isRowAvailable()) {
@@ -510,7 +510,7 @@ public void process(FacesContext faces, PhaseId phase) {
         try {
             // has children
             if (getChildCount() > 0) {
-                Iterator itr;
+                Iterator<?> itr;
                 UIComponent c;
 
                 Integer begin = getBegin();
@@ -529,7 +529,7 @@ public void process(FacesContext faces, PhaseId phase) {
 
                 // grab renderer
                 String rendererType = getRendererType();
-                Renderer renderer = null;
+                Renderer<?> renderer = null;
                 if (rendererType != null) {
                     renderer = getRenderer(faces);
                 }
@@ -701,7 +701,7 @@ private boolean requiresRowIteration(VisitContext ctx) {
         if (!shouldIterate) {
             FacesContext faces = ctx.getFacesContext();
             String sourceId = BEHAVIOR_SOURCE_PARAM.getValue(faces);
-            boolean containsSource = sourceId != null ? sourceId.startsWith(super.getClientId(faces) + getSeparatorChar(faces)) : false;
+            boolean containsSource = sourceId != null && sourceId.startsWith(super.getClientId(faces) + getSeparatorChar(faces));
             return containsSource;
         } else {
             return shouldIterate;
diff --git a/impl/src/main/java/com/sun/faces/facelets/el/DefaultFunctionMapper.java b/impl/src/main/java/com/sun/faces/facelets/el/DefaultFunctionMapper.java
index 61ab2e9e8f..b8c444a703 100644
--- a/impl/src/main/java/com/sun/faces/facelets/el/DefaultFunctionMapper.java
+++ b/impl/src/main/java/com/sun/faces/facelets/el/DefaultFunctionMapper.java
@@ -41,7 +41,7 @@ public final class DefaultFunctionMapper extends FunctionMapper implements Exter
 
     private static final long serialVersionUID = 1L;
 
-    private Map functions = null;
+    private Map<String,Function> functions = null;
 
     /*
      * (non-Javadoc)
@@ -51,7 +51,7 @@ public final class DefaultFunctionMapper extends FunctionMapper implements Exter
     @Override
     public Method resolveFunction(String prefix, String localName) {
         if (functions != null) {
-            Function f = (Function) functions.get(prefix + ":" + localName);
+            Function f = functions.get(prefix + ':' + localName);
             return f.getMethod();
         }
         return null;
@@ -59,7 +59,7 @@ public Method resolveFunction(String prefix, String localName) {
 
     public void addFunction(String prefix, String localName, Method m) {
         if (functions == null) {
-            functions = new HashMap();
+            functions = new HashMap<>();
         }
         Function f = new Function(prefix, localName, m);
         synchronized (this) {
@@ -84,15 +84,15 @@ public void writeExternal(ObjectOutput out) throws IOException {
      */
     @Override
     public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
-        functions = (Map) in.readObject();
+        functions = (Map<String,Function>) in.readObject();
     }
 
     @Override
     public String toString() {
-        StringBuffer sb = new StringBuffer(128);
+        StringBuilder sb = new StringBuilder(128);
         sb.append("FunctionMapper[\n");
-        for (Iterator itr = functions.values().iterator(); itr.hasNext();) {
-            sb.append(itr.next()).append('\n');
+        for (Object o : functions.values()) {
+            sb.append(o).append('\n');
         }
         sb.append(']');
         return sb.toString();
@@ -215,7 +215,7 @@ public int hashCode() {
 
         @Override
         public String toString() {
-            StringBuffer sb = new StringBuffer(32);
+            StringBuilder sb = new StringBuilder(32);
             sb.append("Function[");
             if (prefix != null) {
                 sb.append(prefix).append(':');
diff --git a/impl/src/main/java/com/sun/faces/facelets/el/ELText.java b/impl/src/main/java/com/sun/faces/facelets/el/ELText.java
index d5eb54c1b6..83e567dce2 100644
--- a/impl/src/main/java/com/sun/faces/facelets/el/ELText.java
+++ b/impl/src/main/java/com/sun/faces/facelets/el/ELText.java
@@ -87,12 +87,12 @@ public <T> T getValue(ELContext context) {
         }
 
         @Override
-        public Class getType(ELContext context) {
+        public Class<?> getType(ELContext context) {
             return null;
         }
 
         @Override
-        public Class getExpectedType() {
+        public Class<?> getExpectedType() {
             return null;
         }
 
@@ -108,23 +108,23 @@ public ELTextComposite(ELText[] txt) {
 
         @Override
         public void write(Writer out, ELContext ctx) throws ELException, IOException {
-            for (int i = 0; i < txt.length; i++) {
-                txt[i].write(out, ctx);
+            for (ELText elText : txt) {
+                elText.write(out, ctx);
             }
         }
 
         @Override
         public void writeText(ResponseWriter out, ELContext ctx) throws ELException, IOException {
-            for (int i = 0; i < txt.length; i++) {
-                txt[i].writeText(out, ctx);
+            for (ELText elText : txt) {
+                elText.writeText(out, ctx);
             }
         }
 
         @Override
         public String toString(ELContext ctx) {
-            StringBuffer sb = new StringBuffer();
-            for (int i = 0; i < txt.length; i++) {
-                sb.append(txt[i].toString(ctx));
+            StringBuilder sb = new StringBuilder( 8 * txt.length);
+            for (ELText elText : txt) {
+                sb.append(elText.toString(ctx));
             }
             return sb.toString();
         }
@@ -136,9 +136,9 @@ public String toString(ELContext ctx) {
 
         @Override
         public String toString() {
-            StringBuffer sb = new StringBuffer();
-            for (int i = 0; i < txt.length; i++) {
-                sb.append(txt[i].toString());
+            StringBuilder sb = new StringBuilder( 8 * txt.length);
+            for (ELText elText : txt) {
+                sb.append(elText.toString());
             }
             return sb.toString();
         }
@@ -324,7 +324,7 @@ public static ELText parse(ExpressionFactory fact, ELContext ctx, String in, Str
         boolean esc = false;
         int vlen = 0;
 
-        StringBuffer buff = new StringBuffer(128);
+        StringBuilder buff = new StringBuilder(128);
         List<ELText> text = new ArrayList<>();
         ELText t = null;
         ValueExpression ve = null;
@@ -387,7 +387,7 @@ public static ELText parse(ExpressionFactory fact, ELContext ctx, String in, Str
         } else if (text.size() == 1) {
             return text.get(0);
         } else {
-            ELText[] ta = text.toArray(new ELText[text.size()]);
+            ELText[] ta = text.toArray(new ELText[0]);
             return new ELTextComposite(ta);
         }
     }
diff --git a/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletContext.java b/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletContext.java
index b7a995b8e7..3f61184f56 100644
--- a/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletContext.java
+++ b/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletContext.java
@@ -204,8 +204,8 @@ public String generateUniqueId(String base) {
 
         if (prefix == null) {
             StringBuilder builder = new StringBuilder(faceletHierarchy.size() * 30);
-            for (int i = 0; i < faceletHierarchy.size(); i++) {
-                DefaultFacelet facelet = (DefaultFacelet) faceletHierarchy.get(i);
+            for (Facelet value : faceletHierarchy) {
+                DefaultFacelet facelet = (DefaultFacelet) value;
                 builder.append(facelet.getAlias());
             }
             Integer prefixInt = builder.toString().hashCode();
@@ -215,7 +215,7 @@ public String generateUniqueId(String base) {
                 prefixes.put(prefixInt, 0);
                 prefix = prefixInt.toString();
             } else {
-                int i = cnt.intValue() + 1;
+                int i = cnt + 1;
                 prefixes.put(prefixInt, i);
                 prefix = prefixInt + "_" + i;
             }
@@ -230,7 +230,7 @@ public String generateUniqueId(String base) {
             uniqueIdBuilder.append(base);
             return uniqueIdBuilder.toString();
         } else {
-            int i = cnt.intValue() + 1;
+            int i = cnt + 1;
             ids.put(base, i);
             uniqueIdBuilder.delete(0, uniqueIdBuilder.length());
             uniqueIdBuilder.append(prefix);
@@ -294,7 +294,7 @@ public ELResolver getELResolver() {
     @Override
     public void popClient(TemplateClient client) {
         if (!clients.isEmpty()) {
-            Iterator itr = clients.iterator();
+            Iterator<TemplateManager> itr = clients.iterator();
             while (itr.hasNext()) {
                 if (itr.next().equals(client)) {
                     itr.remove();
diff --git a/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletFactory.java b/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletFactory.java
index b0678ebcb4..c578978c45 100644
--- a/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletFactory.java
+++ b/impl/src/main/java/com/sun/faces/facelets/impl/DefaultFaceletFactory.java
@@ -39,6 +39,7 @@
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
+import java.util.function.Function;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import java.util.regex.Pattern;
diff --git a/impl/src/main/java/com/sun/faces/facelets/impl/DefaultResourceResolver.java b/impl/src/main/java/com/sun/faces/facelets/impl/DefaultResourceResolver.java
index 7cde391063..6ae5f6c38b 100644
--- a/impl/src/main/java/com/sun/faces/facelets/impl/DefaultResourceResolver.java
+++ b/impl/src/main/java/com/sun/faces/facelets/impl/DefaultResourceResolver.java
@@ -24,7 +24,7 @@
 
 public class DefaultResourceResolver {
 
-    private ResourceHandler resourceHandler;
+    private final ResourceHandler resourceHandler;
 
     public DefaultResourceResolver(ResourceHandler resourceHandler) {
         this.resourceHandler = resourceHandler;
diff --git a/impl/src/main/java/com/sun/faces/facelets/impl/FaceletCacheFactoryImpl.java b/impl/src/main/java/com/sun/faces/facelets/impl/FaceletCacheFactoryImpl.java
index ceac74dacc..34a5767d20 100644
--- a/impl/src/main/java/com/sun/faces/facelets/impl/FaceletCacheFactoryImpl.java
+++ b/impl/src/main/java/com/sun/faces/facelets/impl/FaceletCacheFactoryImpl.java
@@ -35,9 +35,8 @@ public FaceletCache getFaceletCache() {
         WebConfiguration webConfig = WebConfiguration.getInstance();
         String refreshPeriod = webConfig.getOptionValue(WebConfiguration.WebContextInitParameter.FaceletsDefaultRefreshPeriod);
         long period = Long.parseLong(refreshPeriod) * 1000;
-        FaceletCache<DefaultFacelet> result = new DefaultFaceletCache(period);
+        FaceletCache result = new DefaultFaceletCache(period);
         return result;
-
     }
 
 }
diff --git a/impl/src/main/java/com/sun/faces/facelets/impl/IdMapper.java b/impl/src/main/java/com/sun/faces/facelets/impl/IdMapper.java
index c3156a8929..09879e8872 100644
--- a/impl/src/main/java/com/sun/faces/facelets/impl/IdMapper.java
+++ b/impl/src/main/java/com/sun/faces/facelets/impl/IdMapper.java
@@ -17,6 +17,7 @@
 package com.sun.faces.facelets.impl;
 
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
 
 import com.sun.faces.util.Cache;
 import com.sun.faces.util.Util;
@@ -24,13 +25,13 @@
 import jakarta.faces.context.FacesContext;
 
 /**
- * Used to provide aliases to Facelets generated unique IDs with tend to be womewhat long.
+ * Used to provide aliases to Facelets generated unique IDs with tend to be somewhat long.
  */
 public class IdMapper {
 
     private static final String KEY = IdMapper.class.getName();
 
-    private Cache<String, String> idCache = new Cache<>(new IdGen());
+    private final Cache<String, String> idCache = new Cache<>(new IdGen());
 
     // ------------------------------------------------------------ Constructors
 
@@ -67,7 +68,7 @@ public static IdMapper getMapper(FacesContext ctx) {
 
     private static final class IdGen implements Cache.Factory<String, String> {
 
-        private AtomicInteger counter = new AtomicInteger(0);
+        private final AtomicInteger counter = new AtomicInteger(0);
 
         // ------------------------------------------ Methods from Cache.Factory
 
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/TagAttributesImpl.java b/impl/src/main/java/com/sun/faces/facelets/tag/TagAttributesImpl.java
index 062b0f34f1..3fb35c121b 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/TagAttributesImpl.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/TagAttributesImpl.java
@@ -44,6 +44,11 @@ public final class TagAttributesImpl extends TagAttributes {
 
     private Tag tag;
 
+    //
+    // todo: why don't use a TreeMap<String,Map<String,TagAttribute> attrsByNamespaceByLocalName ?
+    //       stream(attrs).groupingBy(TagAttribute::getNamespace,TreeMap::new , .... )
+    //
+
     /**
      *
      */
@@ -106,13 +111,14 @@ public TagAttribute get(String localName) {
      */
     @Override
     public TagAttribute get(String ns, String localName) {
+        // todo: with the TreeMap would be a  map.get(namespace).get(localName)
         if (ns != null && localName != null) {
             int idx = Arrays.binarySearch(this.ns, ns);
             if (idx >= 0) {
                 TagAttribute[] uia = (TagAttribute[]) nsattrs.get(idx);
-                for (int i = 0; i < uia.length; i++) {
-                    if (localName.equals(uia[i].getLocalName())) {
-                        return uia[i];
+                for (TagAttribute tagAttribute : uia) {
+                    if (localName.equals(tagAttribute.getLocalName())) {
+                        return tagAttribute;
                     }
                 }
             }
@@ -170,9 +176,9 @@ public void setTag(Tag tag) {
      */
     @Override
     public String toString() {
-        StringBuffer sb = new StringBuffer();
-        for (int i = 0; i < attrs.length; i++) {
-            sb.append(attrs[i]);
+        StringBuilder sb = new StringBuilder();
+        for (TagAttribute attr : attrs) {
+            sb.append(attr);
             sb.append(' ');
         }
         if (sb.length() > 1) {
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/composite/BehaviorHolderWrapper.java b/impl/src/main/java/com/sun/faces/facelets/tag/composite/BehaviorHolderWrapper.java
index a0f89fe76d..5c5a0a975d 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/composite/BehaviorHolderWrapper.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/composite/BehaviorHolderWrapper.java
@@ -16,12 +16,9 @@
 
 package com.sun.faces.facelets.tag.composite;
 
-import static java.util.Collections.unmodifiableMap;
-
 import java.io.IOException;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -408,12 +405,12 @@ protected FacesContext getFacesContext() {
     }
 
     @Override
-    protected FacesListener[] getFacesListeners(Class clazz) {
+    protected FacesListener[] getFacesListeners(Class<?> clazz) {
         return new FacesListener[0];
     }
 
     @Override
-    protected Renderer getRenderer(FacesContext context) {
+    protected Renderer<? extends UIComponent> getRenderer(FacesContext context) {
         return null;
     }
 
@@ -439,10 +436,7 @@ public void addClientBehavior(String eventName, ClientBehavior behavior) {
     public Map<String, List<ClientBehavior>> getClientBehaviors() {
         if (parent instanceof ClientBehaviorHolder) {
             ClientBehaviorHolder parentHolder = (ClientBehaviorHolder) parent;
-            Map<String, List<ClientBehavior>> behaviors = new HashMap<>(1);
-            behaviors.put(virtualEvent, parentHolder.getClientBehaviors().get(event));
-            
-            return unmodifiableMap(behaviors);
+            return Map.of( virtualEvent, parentHolder.getClientBehaviors().get(event)  );
         } 
         
         throw new FacesException("Unable to get behaviors from non-ClientBehaviorHolder parent:" + parent);
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/composite/InterfaceHandler.java b/impl/src/main/java/com/sun/faces/facelets/tag/composite/InterfaceHandler.java
index 52cb6c9d6f..82035896c7 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/composite/InterfaceHandler.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/composite/InterfaceHandler.java
@@ -90,7 +90,7 @@ private void validateComponent(FacesContext context, UIComponent ccParent) throw
         String key;
         Object requiredValue;
         boolean found = false, required = false;
-        StringBuffer buf = null;
+        StringBuilder buf = null;
         String attrMessage = "", facetMessage = "";
 
         // Traverse the attributes of this component
@@ -121,7 +121,7 @@ private void validateComponent(FacesContext context, UIComponent ccParent) throw
                 }
                 if (!found) {
                     if (null == buf) {
-                        buf = new StringBuffer();
+                        buf = new StringBuilder();
                         buf.append(key);
                     } else {
                         buf.append(", " + key);
@@ -152,7 +152,7 @@ private void validateComponent(FacesContext context, UIComponent ccParent) throw
                     key = cur.getName();
                     if (!cc.getFacets().containsKey(key)) {
                         if (null == buf) {
-                            buf = new StringBuffer();
+                            buf = new StringBuilder();
                             buf.append(key);
                         } else {
                             buf.append(", " + key);
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/faces/BehaviorTagHandlerDelegateImpl.java b/impl/src/main/java/com/sun/faces/facelets/tag/faces/BehaviorTagHandlerDelegateImpl.java
index a92ac93dd7..66cb1bae4d 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/faces/BehaviorTagHandlerDelegateImpl.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/faces/BehaviorTagHandlerDelegateImpl.java
@@ -131,7 +131,7 @@ public void applyAttachedObject(FacesContext context, UIComponent parent) {
     }
 
     @Override
-    public MetaRuleset createMetaRuleset(Class type) {
+    public MetaRuleset createMetaRuleset(Class<?> type) {
         Util.notNull("type", type);
         MetaRuleset m = new MetaRulesetImpl(owner.getTag(), type);
         m = m.ignore("event");
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/faces/ComponentTagHandlerDelegateImpl.java b/impl/src/main/java/com/sun/faces/facelets/tag/faces/ComponentTagHandlerDelegateImpl.java
index 4a9b9c1637..8221c6b543 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/faces/ComponentTagHandlerDelegateImpl.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/faces/ComponentTagHandlerDelegateImpl.java
@@ -260,7 +260,7 @@ private void adjustIndexOfDynamicChildren(FacesContext context, UIComponent pare
     }
 
     @Override
-    public MetaRuleset createMetaRuleset(Class type) {
+    public MetaRuleset createMetaRuleset(Class<?> type) {
         Util.notNull("type", type);
         MetaRuleset m = new MetaRulesetImpl(owner.getTag(), type);
 
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/faces/ConverterTagHandlerDelegateImpl.java b/impl/src/main/java/com/sun/faces/facelets/tag/faces/ConverterTagHandlerDelegateImpl.java
index c127e8bb49..12702bcad7 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/faces/ConverterTagHandlerDelegateImpl.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/faces/ConverterTagHandlerDelegateImpl.java
@@ -69,7 +69,7 @@ public void apply(FaceletContext ctx, UIComponent parent) throws IOException {
     }
 
     @Override
-    public MetaRuleset createMetaRuleset(Class type) {
+    public MetaRuleset createMetaRuleset(Class<?> type) {
         Util.notNull("type", type);
         MetaRuleset m = new MetaRulesetImpl(owner.getTag(), type);
 
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/faces/ValidatorTagHandlerDelegateImpl.java b/impl/src/main/java/com/sun/faces/facelets/tag/faces/ValidatorTagHandlerDelegateImpl.java
index 8764ba95e5..9d22944691 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/faces/ValidatorTagHandlerDelegateImpl.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/faces/ValidatorTagHandlerDelegateImpl.java
@@ -71,7 +71,7 @@ public void apply(FaceletContext ctx, UIComponent parent) throws IOException {
     }
 
     @Override
-    public MetaRuleset createMetaRuleset(Class type) {
+    public MetaRuleset createMetaRuleset(Class<?> type) {
 
         Util.notNull("type", type);
         MetaRuleset m = new MetaRulesetImpl(owner.getTag(), type);
diff --git a/impl/src/main/java/com/sun/faces/facelets/tag/ui/UIDebug.java b/impl/src/main/java/com/sun/faces/facelets/tag/ui/UIDebug.java
index 5a5d436f16..13255c3ba1 100644
--- a/impl/src/main/java/com/sun/faces/facelets/tag/ui/UIDebug.java
+++ b/impl/src/main/java/com/sun/faces/facelets/tag/ui/UIDebug.java
@@ -18,7 +18,6 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -27,6 +26,7 @@
 import com.sun.faces.renderkit.RenderKitUtils;
 import com.sun.faces.renderkit.html_basic.ScriptRenderer;
 
+import com.sun.faces.util.LRUMap;
 import jakarta.faces.component.UIComponentBase;
 import jakarta.faces.context.FacesContext;
 import jakarta.faces.context.ResponseWriter;
@@ -80,7 +80,7 @@ public void encodeBegin(FacesContext facesContext) throws IOException {
             pushComponentToEL(facesContext, this);
             String actionId = facesContext.getApplication().getViewHandler().getActionURL(facesContext, facesContext.getViewRoot().getViewId());
 
-            StringBuffer sb = new StringBuffer(512);
+            StringBuilder sb = new StringBuilder(512);
             sb.append("//<![CDATA[\n");
             sb.append("function faceletsDebugWindow(URL) {");
             sb.append("day = new Date();");
@@ -119,27 +119,19 @@ private static String writeDebugOutput(FacesContext faces) throws IOException {
         FastWriter fw = new FastWriter();
         DevTools.debugHtml(fw, faces);
 
-        Map session = faces.getExternalContext().getSessionMap();
+        Map<String, Object> session = faces.getExternalContext().getSessionMap();
         Map debugs = (Map) session.get(KEY);
         if (debugs == null) {
-            debugs = new LinkedHashMap() {
-
-                private static final long serialVersionUID = 2541609242499547693L;
-
-                @Override
-                protected boolean removeEldestEntry(Map.Entry eldest) {
-                    return size() > 5;
-                }
-            };
+            debugs = new LRUMap<>(5);
         }
         session.put(KEY, debugs);
-        String id = "" + nextId++;
+        String id = String.valueOf(nextId++);
         debugs.put(id, fw.toString());
         return id;
     }
 
     private static String fetchDebugOutput(FacesContext faces, String id) {
-        Map session = faces.getExternalContext().getSessionMap();
+        Map<String, Object> session = faces.getExternalContext().getSessionMap();
         Map debugs = (Map) session.get(KEY);
         if (debugs != null) {
             return (String) debugs.get(id);
diff --git a/impl/src/main/java/com/sun/faces/facelets/util/Classpath.java b/impl/src/main/java/com/sun/faces/facelets/util/Classpath.java
index ac2bbce3b3..cf613d9d7a 100644
--- a/impl/src/main/java/com/sun/faces/facelets/util/Classpath.java
+++ b/impl/src/main/java/com/sun/faces/facelets/util/Classpath.java
@@ -23,6 +23,7 @@
 import java.net.URL;
 import java.net.URLConnection;
 import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
 import java.util.Enumeration;
 import java.util.LinkedHashSet;
 import java.util.Set;
@@ -65,20 +66,20 @@ public static URL[] search(ClassLoader cl, String prefix, String suffix) throws
     }
 
     public static URL[] search(ClassLoader cl, String prefix, String suffix, SearchAdvice advice) throws IOException {
-        Enumeration[] e = new Enumeration[] { cl.getResources(prefix), cl.getResources(prefix + "MANIFEST.MF") };
-        Set all = new LinkedHashSet();
+        Enumeration<URL>[] e = new Enumeration[] { cl.getResources(prefix), cl.getResources(prefix + "MANIFEST.MF") };
+        Set<URL> all = new LinkedHashSet<>();
         URL url;
         URLConnection conn;
         JarFile jarFile;
-        for (int i = 0, s = e.length; i < s; ++i) {
-            while (e[i].hasMoreElements()) {
-                url = (URL) e[i].nextElement();
+        for (Enumeration<URL> urlEnumeration : e) {
+            while (urlEnumeration.hasMoreElements()) {
+                url = urlEnumeration.nextElement();
                 // Defensive programming. Due to issue 13045 this collection
                 // can contain URLs that have their spaces incorrectly escaped
                 // by having %20 replaced with %2520. This quick conditional
                 // check catches this particular case and averts it.
                 String str = url.getPath();
-                if (-1 != str.indexOf("%2520")) {
+                if (str.contains("%2520")) {
                     str = url.toExternalForm();
                     str = str.replace("%2520", "%20");
                     url = new URL(str);
@@ -93,18 +94,18 @@ public static URL[] search(ClassLoader cl, String prefix, String suffix, SearchA
                 if (jarFile != null) {
                     searchJar(cl, all, jarFile, prefix, suffix, advice);
                 } else {
-                    boolean searchDone = searchDir(all, new File(URLDecoder.decode(url.getFile(), "UTF-8")), suffix);
+                    boolean searchDone = searchDir(all, new File(URLDecoder.decode(url.getFile(), StandardCharsets.UTF_8)), suffix);
                     if (!searchDone) {
                         searchFromURL(all, prefix, suffix, url);
                     }
                 }
             }
         }
-        URL[] urlArray = (URL[]) all.toArray(new URL[all.size()]);
+        URL[] urlArray = all.toArray(new URL[0]);
         return urlArray;
     }
 
-    private static boolean searchDir(Set result, File file, String suffix) throws IOException {
+    private static boolean searchDir(Set<URL> result, File file, String suffix) throws IOException {
         if (file.exists() && file.isDirectory()) {
             File[] fc = file.listFiles();
             String path;
@@ -115,13 +116,13 @@ private static boolean searchDir(Set result, File file, String suffix) throws IO
                 return false;
             }
 
-            for (int i = 0; i < fc.length; i++) {
-                path = fc[i].getAbsolutePath();
-                if (fc[i].isDirectory()) {
-                    searchDir(result, fc[i], suffix);
+            for (File value : fc) {
+                path = value.getAbsolutePath();
+                if (value.isDirectory()) {
+                    searchDir(result, value, suffix);
                 } else if (path.endsWith(suffix)) {
                     // result.add(new URL("file:/" + path));
-                    result.add(fc[i].toURL());
+                    result.add(value.toURL());
                 }
             }
             return true;
@@ -139,7 +140,7 @@ private static boolean searchDir(Set result, File file, String suffix) throws IO
      *
      * @throws IOException for any error
      */
-    private static void searchFromURL(Set result, String prefix, String suffix, URL url) throws IOException {
+    private static void searchFromURL(Set<URL> result, String prefix, String suffix, URL url) throws IOException {
         boolean done = false;
         InputStream is = getInputStream(url);
         if (is != null) {
@@ -182,7 +183,7 @@ private static void searchFromURL(Set result, String prefix, String suffix, URL
     }
 
     /**
-     * Join tokens, exlude last if param equals true.
+     * Join tokens, exclude last if param equals true.
      *
      * @param tokens the tokens
      * @param excludeLast do we exclude last token
@@ -190,7 +191,7 @@ private static void searchFromURL(Set result, String prefix, String suffix, URL
      * @return joined tokens
      */
     private static String join(String[] tokens, boolean excludeLast) {
-        StringBuffer join = new StringBuffer();
+        StringBuilder join = new StringBuilder();
         for (int i = 0; i < tokens.length - (excludeLast ? 1 : 0); i++) {
             join.append(tokens[i]).append("/");
         }
@@ -244,7 +245,7 @@ static JarFile getAlternativeJarFile(String urlFile) throws IOException {
             // And trim off any "file:" prefix.
             if (jarFileUrl.startsWith("file:")) {
                 jarFileUrl = jarFileUrl.substring("file:".length());
-                jarFileUrl = URLDecoder.decode(jarFileUrl, "UTF-8");
+                jarFileUrl = URLDecoder.decode(jarFileUrl, StandardCharsets.UTF_8);
             }
             boolean foundExclusion = false;
             for (int i = 0; i < PREFIXES_TO_EXCLUDE.length; i++) {
@@ -266,19 +267,19 @@ static JarFile getAlternativeJarFile(String urlFile) throws IOException {
         return null;
     }
 
-    private static void searchJar(ClassLoader cl, Set result, JarFile file, String prefix, String suffix, SearchAdvice advice) throws IOException {
-        Enumeration e = file.entries();
+    private static void searchJar(ClassLoader cl, Set<URL> result, JarFile file, String prefix, String suffix, SearchAdvice advice) throws IOException {
+        Enumeration<JarEntry> e = file.entries();
         JarEntry entry;
         String name;
         while (e.hasMoreElements()) {
             try {
-                entry = (JarEntry) e.nextElement();
+                entry = e.nextElement();
             } catch (Throwable t) {
                 continue;
             }
             name = entry.getName();
             if (name.startsWith(prefix) && name.endsWith(suffix)) {
-                Enumeration e2 = cl.getResources(name);
+                Enumeration<URL> e2 = cl.getResources(name);
                 while (e2.hasMoreElements()) {
                     result.add(e2.nextElement());
                     if (advice == SearchAdvice.FirstMatchOnly) {
diff --git a/impl/src/main/java/com/sun/faces/facelets/util/ReflectionUtil.java b/impl/src/main/java/com/sun/faces/facelets/util/ReflectionUtil.java
index fc207039d2..341b59dbd9 100644
--- a/impl/src/main/java/com/sun/faces/facelets/util/ReflectionUtil.java
+++ b/impl/src/main/java/com/sun/faces/facelets/util/ReflectionUtil.java
@@ -146,11 +146,11 @@ public static String[] toTypeNameArray(Class[] c) {
 //        return null;
 //    }
 
-    protected static final String paramString(Class[] types) {
+    protected static String paramString(Class<?>[] types) {
         if (types != null) {
-            StringBuffer sb = new StringBuffer();
-            for (int i = 0; i < types.length; i++) {
-                sb.append(types[i].getName()).append(", ");
+            StringBuilder sb = new StringBuilder();
+            for (Class<?> type : types) {
+                sb.append(type.getName()).append(", ");
             }
             if (sb.length() > 2) {
                 sb.setLength(sb.length() - 2);
@@ -163,14 +163,12 @@ protected static final String paramString(Class[] types) {
     public static Object decorateInstance(Class clazz, Class rootType, Object root) {
         Object returnObject = null;
         try {
-            if (returnObject == null) {
-                // Look for an adapter constructor if we've got
-                // an object to adapt
-                if (rootType != null && root != null) {
-                    Constructor construct = ReflectionUtils.lookupConstructor(clazz, rootType);
-                    if (construct != null) {
-                        returnObject = construct.newInstance(root);
-                    }
+            // Look for an adapter constructor if we've got
+            // an object to adapt
+            if (rootType != null && root != null) {
+                Constructor construct = ReflectionUtils.lookupConstructor(clazz, rootType);
+                if (construct != null) {
+                    returnObject = construct.newInstance(root);
                 }
             }
             if (clazz != null && returnObject == null) {
diff --git a/impl/src/main/java/com/sun/faces/renderkit/AttributeManager.java b/impl/src/main/java/com/sun/faces/renderkit/AttributeManager.java
index 091d63e887..28d3113a7f 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/AttributeManager.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/AttributeManager.java
@@ -40,7 +40,7 @@ public enum Key {
         OUTPUTBODY, OUTPUTDOCTYPE, OUTPUTHEAD;
     }
 
-    private static Map<Key, Attribute[]> ATTRIBUTE_LOOKUP = CollectionsUtils.<Key, Attribute[]>map()
+    private static final Map<Key, Attribute[]> ATTRIBUTE_LOOKUP = CollectionsUtils.<Key, Attribute[]>map()
             .add(Key.COMMANDBUTTON,
                     ar(attr("accesskey"), attr("dir"), attr("lang"), attr("onblur", "blur"), attr("onchange", "change"), attr("ondblclick", "dblclick"),
                         attr("onfocus", "focus"), attr("onkeydown", "keydown"), attr("onkeypress", "keypress"), attr("onkeyup", "keyup"),
diff --git a/impl/src/main/java/com/sun/faces/renderkit/RenderKitImpl.java b/impl/src/main/java/com/sun/faces/renderkit/RenderKitImpl.java
index 13c1000810..681514423c 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/RenderKitImpl.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/RenderKitImpl.java
@@ -42,6 +42,7 @@
 import com.sun.faces.util.MessageUtils;
 import com.sun.faces.util.Util;
 
+import jakarta.faces.component.UIComponent;
 import jakarta.faces.context.FacesContext;
 import jakarta.faces.context.ResponseStream;
 import jakarta.faces.context.ResponseWriter;
@@ -70,17 +71,17 @@ public class RenderKitImpl extends RenderKit {
      * Keys are String renderer family. Values are HashMaps. Nested HashMap keys are Strings for the rendererType, and
      * values are the Renderer instances themselves.
      */
-    private ConcurrentHashMap<String, HashMap<String, Renderer>> rendererFamilies = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<String, HashMap<String, Renderer<? extends UIComponent>>> rendererFamilies = new ConcurrentHashMap<>();
 
     /**
      * For Behavior Renderers: Keys are Strings for the behaviorRendererType, and values are the behaviorRenderer instances
      * themselves.
      */
-    private ConcurrentHashMap<String, ClientBehaviorRenderer> behaviorRenderers = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<String, ClientBehaviorRenderer> behaviorRenderers = new ConcurrentHashMap<>();
 
     private ResponseStateManager responseStateManager = new ResponseStateManagerImpl();
 
-    private WebConfiguration webConfig;
+    private final WebConfiguration webConfig;
 
     public RenderKitImpl() {
 
@@ -90,17 +91,13 @@ public RenderKitImpl() {
     }
 
     @Override
-    public void addRenderer(String family, String rendererType, Renderer renderer) {
+    public void addRenderer(String family, String rendererType, Renderer<? extends UIComponent> renderer) {
 
         Util.notNull("family", family);
         Util.notNull("rendererType", rendererType);
         Util.notNull("renderer", renderer);
 
-        HashMap<String, Renderer> renderers = rendererFamilies.get(family);
-        if (renderers == null) {
-            renderers = new HashMap<>();
-            rendererFamilies.put(family, renderers);
-        }
+        Map<String, Renderer<? extends UIComponent>> renderers = rendererFamilies.computeIfAbsent(family, k -> new HashMap<>());
 
         if (LOGGER.isLoggable(Level.FINE) && renderers.containsKey(rendererType)) {
             LOGGER.log(Level.FINE, "rendererType {0} has already been registered for family {1}.  Replacing existing renderer class type {2} with {3}.",
@@ -111,14 +108,14 @@ public void addRenderer(String family, String rendererType, Renderer renderer) {
     }
 
     @Override
-    public Renderer getRenderer(String family, String rendererType) {
+    public Renderer<? extends UIComponent> getRenderer(String family, String rendererType) {
 
         Util.notNull("family", family);
         Util.notNull("rendererType", rendererType);
 
-        assert rendererFamilies != null;
+        assert rendererFamilies != null; // ??
 
-        HashMap<String, Renderer> renderers = rendererFamilies.get(family);
+        Map<String, Renderer<? extends UIComponent>> renderers = rendererFamilies.get(family);
         return renderers != null ? renderers.get(rendererType) : null;
 
     }
@@ -143,16 +140,12 @@ public ClientBehaviorRenderer getClientBehaviorRenderer(String behaviorRendererT
 
         Util.notNull("behaviorRendererType", behaviorRendererType);
 
-        return behaviorRenderers != null ? behaviorRenderers.get(behaviorRendererType) : null;
+        return behaviorRenderers.get(behaviorRendererType);
 
     }
 
     @Override
     public Iterator<String> getClientBehaviorRendererTypes() {
-        if (null == behaviorRenderers) {
-            Set<String> empty = Collections.emptySet();
-            return empty.iterator();
-        }
         return behaviorRenderers.keySet().iterator();
     }
 
@@ -198,7 +191,7 @@ public ResponseWriter createResponseWriter(Writer writer, String desiredContentT
         if (null == desiredContentTypeList || contentTypeNullFromResponse) {
             String[] typeArray = context.getExternalContext().getRequestHeaderValuesMap().get("Accept");
             if (typeArray.length > 0) {
-                StringBuffer buff = new StringBuffer();
+                StringBuilder buff = new StringBuilder();
                 buff.append(typeArray[0]);
                 for (int i = 1, len = typeArray.length; i < len; i++) {
                     buff.append(',');
@@ -279,15 +272,13 @@ private String findMatch(String desiredContentTypeList, String[] supportedTypes)
 
         // For each entry in the desiredTypes array, look for a match in
         // the supportedTypes array
-        for (int i = 0, ilen = desiredTypes.length; i < ilen; i++) {
-            String curDesiredType = desiredTypes[i];
-            for (int j = 0, jlen = supportedTypes.length; j < jlen; j++) {
-                String curContentType = supportedTypes[j].trim();
+        for (String curDesiredType : desiredTypes) {
+            for (String supportedType : supportedTypes) {
+                String curContentType = supportedType.trim();
                 if (curDesiredType.contains(curContentType)) {
                     if (curContentType.contains(RIConstants.HTML_CONTENT_TYPE)) {
                         contentType = RIConstants.HTML_CONTENT_TYPE;
-                    } else if (curContentType.contains(RIConstants.XHTML_CONTENT_TYPE) || curContentType.contains(RIConstants.APPLICATION_XML_CONTENT_TYPE)
-                            || curContentType.contains(RIConstants.TEXT_XML_CONTENT_TYPE)) {
+                    } else if (curContentType.contains(RIConstants.XHTML_CONTENT_TYPE) || curContentType.contains(RIConstants.APPLICATION_XML_CONTENT_TYPE) || curContentType.contains(RIConstants.TEXT_XML_CONTENT_TYPE)) {
                         contentType = RIConstants.XHTML_CONTENT_TYPE;
                     }
                     break;
@@ -310,12 +301,12 @@ public void write(int b) throws IOException {
             }
 
             @Override
-            public void write(byte b[]) throws IOException {
+            public void write(byte[] b) throws IOException {
                 output.write(b);
             }
 
             @Override
-            public void write(byte b[], int off, int len) throws IOException {
+            public void write(byte[] b, int off, int len) throws IOException {
                 output.write(b, off, len);
             }
 
@@ -347,12 +338,11 @@ public Iterator<String> getComponentFamilies() {
     @Override
     public Iterator<String> getRendererTypes(String componentFamily) {
 
-        Map<String, Renderer> family = rendererFamilies.get(componentFamily);
+        Map<String, Renderer<? extends UIComponent>> family = rendererFamilies.get(componentFamily);
         if (family != null) {
             return family.keySet().iterator();
         } else {
-            Set<String> empty = Collections.emptySet();
-            return empty.iterator();
+            return Collections.emptyIterator();
         }
 
     }
diff --git a/impl/src/main/java/com/sun/faces/renderkit/html_basic/HtmlBasicRenderer.java b/impl/src/main/java/com/sun/faces/renderkit/html_basic/HtmlBasicRenderer.java
index 2c56873c9a..883c73b399 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/html_basic/HtmlBasicRenderer.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/html_basic/HtmlBasicRenderer.java
@@ -44,6 +44,7 @@
 import com.sun.faces.util.MessageUtils;
 import com.sun.faces.util.Util;
 
+import jakarta.faces.application.FacesMessage;
 import jakarta.faces.component.NamingContainer;
 import jakarta.faces.component.UIComponent;
 import jakarta.faces.component.UIInput;
@@ -278,7 +279,7 @@ protected Iterator<UIComponent> getChildren(UIComponent component) {
         if (childCount > 0) {
             return component.getChildren().iterator();
         } else {
-            return Collections.<UIComponent>emptyList().iterator();
+            return Collections.emptyIterator();
         }
 
     }
@@ -467,7 +468,7 @@ protected String getFormattedValue(FacesContext context, UIComponent component,
     private static final Set<SearchExpressionHint> EXPRESSION_HINTS = EnumSet.of(SearchExpressionHint.IGNORE_NO_RESULT,
             SearchExpressionHint.RESOLVE_SINGLE_COMPONENT);
 
-    protected Iterator getMessageIter(FacesContext context, String forComponent, UIComponent component) {
+    protected Iterator<FacesMessage> getMessageIter(FacesContext context, String forComponent, UIComponent component) {
         // no "for" expression - return all messages
         if (forComponent == null) {
             return context.getMessages();
@@ -510,7 +511,7 @@ protected Param[] getParamList(UIComponent command) {
                     }
                 }
             }
-            return parameterList.toArray(new Param[parameterList.size()]);
+            return parameterList.toArray(new Param[0]);
         } else {
             return EMPTY_PARAMS;
         }
@@ -550,7 +551,7 @@ protected Collection<ClientBehaviorContext.Parameter> getBehaviorParameters(UICo
             }
         }
 
-        return params == null ? Collections.<ClientBehaviorContext.Parameter>emptyList() : params;
+        return params == null ? Collections.emptyList() : params;
     }
 
     protected Object getValue(UIComponent component) {
@@ -708,9 +709,7 @@ private static UIComponent findUIComponentBelow(UIComponent startPoint, String f
         UIComponent retComp = null;
         if (startPoint.getChildCount() > 0) {
             List<UIComponent> children = startPoint.getChildren();
-            for (int i = 0, size = children.size(); i < size; i++) {
-                UIComponent comp = children.get(i);
-
+            for (UIComponent comp : children) {
                 if (comp instanceof NamingContainer) {
                     try {
                         retComp = comp.findComponent(forComponent);
diff --git a/impl/src/main/java/com/sun/faces/renderkit/html_basic/MenuRenderer.java b/impl/src/main/java/com/sun/faces/renderkit/html_basic/MenuRenderer.java
index 9477b9ae30..3d3edfcc27 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/html_basic/MenuRenderer.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/html_basic/MenuRenderer.java
@@ -791,7 +791,7 @@ protected Collection<Object> createCollectionFromHint(Object collectionTypeHint)
             collectionType = (Class<? extends Collection<Object>>) collectionTypeHint;
         } else if (collectionTypeHint instanceof String) {
             try {
-                collectionType = Util.loadClass((String) collectionTypeHint, this);
+                collectionType = (Class<? extends Collection<Object>>) Util.loadClass((String) collectionTypeHint, this);
             } catch (ClassNotFoundException cnfe) {
                 throw new FacesException(cnfe);
             }
@@ -820,7 +820,7 @@ private void decodeUISelectMany(FacesContext context, UISelectMany component, St
         Map<String, String[]> requestParameterValuesMap = context.getExternalContext().getRequestParameterValuesMap();
 
         if (requestParameterValuesMap.containsKey(clientId)) {
-            String newValues[] = requestParameterValuesMap.get(clientId);
+            String[] newValues = requestParameterValuesMap.get(clientId);
 
             if (newValues != null && newValues.length > 0) {
                 Set<String> disabledSelectItemValues = getDisabledSelectItemValues(context, component);
@@ -828,7 +828,7 @@ private void decodeUISelectMany(FacesContext context, UISelectMany component, St
                     List<String> newValuesList = new ArrayList<>(Arrays.asList(newValues));
 
                     if (newValuesList.removeAll(disabledSelectItemValues)) {
-                        newValues = newValuesList.toArray(new String[newValuesList.size()]);
+                        newValues = newValuesList.toArray(new String[0]);
                     }
                 }
             }
diff --git a/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputLinkRenderer.java b/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputLinkRenderer.java
index 2bb779516d..2232224579 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputLinkRenderer.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputLinkRenderer.java
@@ -23,6 +23,7 @@
 
 import java.io.IOException;
 import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 
 import com.sun.faces.renderkit.Attribute;
 import com.sun.faces.renderkit.AttributeManager;
@@ -166,20 +167,20 @@ protected void renderAsActive(FacesContext context, UIComponent component) throw
 
         // Write Anchor attributes
 
-        Param paramList[] = getParamList(component);
-        StringBuffer sb = new StringBuffer();
+        Param[] paramList = getParamList(component);
+        StringBuilder sb = new StringBuilder();
         sb.append(hrefVal);
         boolean paramWritten = hrefVal.indexOf('?') > 0;
 
-        for (int i = 0, len = paramList.length; i < len; i++) {
-            String pn = paramList[i].name;
+        for (Param param : paramList) {
+            String pn = param.name;
             if (pn != null && pn.length() != 0) {
-                String pv = paramList[i].value;
+                String pv = param.value;
                 sb.append(paramWritten ? '&' : '?');
-                sb.append(URLEncoder.encode(pn, "UTF-8"));
+                sb.append(URLEncoder.encode(pn, StandardCharsets.UTF_8));
                 sb.append('=');
                 if (pv != null && pv.length() != 0) {
-                    sb.append(URLEncoder.encode(pv, "UTF-8"));
+                    sb.append(URLEncoder.encode(pv, StandardCharsets.UTF_8));
                 }
                 paramWritten = true;
             }
diff --git a/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputMessageRenderer.java b/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputMessageRenderer.java
index 69d2e07a3f..345eb70446 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputMessageRenderer.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/html_basic/OutputMessageRenderer.java
@@ -83,7 +83,7 @@ public void encodeEnd(FacesContext context, UIComponent component) throws IOExce
         if (parameterList.size() > 0) {
             MessageFormat fmt = new MessageFormat(currentValue, context.getViewRoot().getLocale());
             StringBuffer buf = new StringBuffer(currentValue.length() * 2);
-            fmt.format(parameterList.toArray(new Object[parameterList.size()]), buf, null);
+            fmt.format(parameterList.toArray(new Object[0]), buf, null);
             message = buf.toString();
         } else {
             message = currentValue;
@@ -121,7 +121,7 @@ public void encodeEnd(FacesContext context, UIComponent component) throws IOExce
         }
 
         Object val = component.getAttributes().get("escape");
-        boolean escape = val != null && Boolean.valueOf(val.toString());
+        boolean escape = val != null && Boolean.parseBoolean(val.toString());
 
         if (escape) {
             writer.writeText(message, component, "value");
diff --git a/impl/src/main/java/com/sun/faces/util/ComponentStruct.java b/impl/src/main/java/com/sun/faces/util/ComponentStruct.java
index f2d7ab5a81..ccdb5c8a86 100644
--- a/impl/src/main/java/com/sun/faces/util/ComponentStruct.java
+++ b/impl/src/main/java/com/sun/faces/util/ComponentStruct.java
@@ -19,6 +19,8 @@
 import jakarta.faces.component.StateHolder;
 import jakarta.faces.context.FacesContext;
 
+import java.util.Objects;
+
 /**
  * Utility class to enable partial state saving of components that have been dynamically added to the view.
  */
@@ -73,7 +75,7 @@ public void restoreState(FacesContext ctx, Object state) {
             return;
         }
 
-        Object s[] = (Object[]) state;
+        Object[] s = (Object[]) state;
         action = (String) s[0];
         parentClientId = (String) s[1];
         clientId = (String) s[2];
@@ -87,7 +89,7 @@ public Object saveState(FacesContext ctx) {
             throw new NullPointerException();
         }
 
-        Object state[] = new Object[5];
+        Object[] state = new Object[5];
         state[0] = action;
         state[1] = parentClientId;
         state[2] = clientId;
diff --git a/impl/src/main/java/com/sun/faces/util/HtmlUtils.java b/impl/src/main/java/com/sun/faces/util/HtmlUtils.java
index 0815690a3d..230d2eb61e 100644
--- a/impl/src/main/java/com/sun/faces/util/HtmlUtils.java
+++ b/impl/src/main/java/com/sun/faces/util/HtmlUtils.java
@@ -167,7 +167,7 @@ static public void writeAttribute(Writer out, boolean escapeUnicode, boolean esc
                     if (ch >= 0x3f) {
                         if (ch == 's') {
                             // If putting scripts in attribute values
-                            // has been disabled (the defualt), look for
+                            // has been disabled (the default), look for
                             // script: in the attribute value.
                             // ensure the attribute value is long enough
                             // to accomodate "script:"
diff --git a/impl/src/main/java/com/sun/faces/util/LRUMap.java b/impl/src/main/java/com/sun/faces/util/LRUMap.java
index dc14511294..82521b304f 100644
--- a/impl/src/main/java/com/sun/faces/util/LRUMap.java
+++ b/impl/src/main/java/com/sun/faces/util/LRUMap.java
@@ -25,7 +25,7 @@
 public class LRUMap<K, V> extends LinkedHashMap<K, V> {
 
     private static final long serialVersionUID = -7137951139094651602L;
-    private int maxCapacity;
+    private final int maxCapacity;
 
     // ------------------------------------------------------------ Constructors
 
diff --git a/impl/src/main/java/com/sun/faces/util/MessageFactory.java b/impl/src/main/java/com/sun/faces/util/MessageFactory.java
index 1e907b6f71..c0ea8865b7 100644
--- a/impl/src/main/java/com/sun/faces/util/MessageFactory.java
+++ b/impl/src/main/java/com/sun/faces/util/MessageFactory.java
@@ -309,7 +309,7 @@ private String getFormattedString(String msgtext, Object[] params) {
             if (params == null || msgtext == null) {
                 return msgtext;
             }
-            StringBuffer b = new StringBuffer(100);
+            StringBuilder b = new StringBuilder(100);
             MessageFormat mf = new MessageFormat(msgtext);
             if (locale != null) {
                 mf.setLocale(locale);
@@ -319,8 +319,8 @@ private String getFormattedString(String msgtext, Object[] params) {
             return localizedStr;
         }
 
-        private Locale locale;
-        private Object[] parameters;
+        private final Locale locale;
+        private final Object[] parameters;
         private Object[] resolvedParameters;
     }
 
diff --git a/impl/src/main/java/com/sun/faces/util/MostlySingletonSet.java b/impl/src/main/java/com/sun/faces/util/MostlySingletonSet.java
index 95f86dc4ee..e77a44346d 100644
--- a/impl/src/main/java/com/sun/faces/util/MostlySingletonSet.java
+++ b/impl/src/main/java/com/sun/faces/util/MostlySingletonSet.java
@@ -63,7 +63,7 @@ public boolean addAll(Collection<? extends E> c) {
         boolean result = true;
 
         if (null == inner && 1 == c.size()) {
-            inner = (Set<E>) Collections.singleton(c.iterator().next());
+            inner = Collections.singleton(c.iterator().next());
         } else {
             // If we need to transition from one to more-than-one
             if (1 == inner.size()) {
@@ -126,7 +126,7 @@ public boolean removeAll(Collection<?> c) {
         if (null != inner) {
             if (1 == inner.size()) {
                 // May throw NPE per spec for Collection.removeAll()
-                Iterator incomingIter = c.iterator();
+                Iterator<?> incomingIter = c.iterator();
                 E oneAndOnlyElement = inner.iterator().next();
                 // Iterate over the incoming collection
                 // looking for a member that is equal to our one and only
diff --git a/impl/src/main/java/com/sun/faces/util/ScopedRunner.java b/impl/src/main/java/com/sun/faces/util/ScopedRunner.java
index 25645a0270..b5ab0de7bb 100644
--- a/impl/src/main/java/com/sun/faces/util/ScopedRunner.java
+++ b/impl/src/main/java/com/sun/faces/util/ScopedRunner.java
@@ -30,9 +30,9 @@
  */
 public class ScopedRunner {
 
-	private FacesContext context;
-	private Map<String, Object> scopedVariables;
-	private Map<String, Object> previousVariables = new HashMap<>();
+	private final FacesContext context;
+	private final Map<String, Object> scopedVariables;
+	private final Map<String, Object> previousVariables = new HashMap<>();
 
 	public ScopedRunner(FacesContext context) {
 		this(context, new HashMap<>());
diff --git a/impl/src/main/java/com/sun/faces/util/Util.java b/impl/src/main/java/com/sun/faces/util/Util.java
index 14c62e2db7..dc10ce6292 100644
--- a/impl/src/main/java/com/sun/faces/util/Util.java
+++ b/impl/src/main/java/com/sun/faces/util/Util.java
@@ -317,7 +317,7 @@ public static SchemaFactory createSchemaFactory(String uri) {
         return factory;
     }
 
-    public static Class loadClass(String name, Object fallbackClass) throws ClassNotFoundException {
+    public static Class<?> loadClass(String name, Object fallbackClass) throws ClassNotFoundException {
         ClassLoader loader = Util.getCurrentLoader(fallbackClass);
 
         String[] primitiveNames = { "byte", "short", "int", "long", "float", "double", "boolean", "char" };
@@ -897,7 +897,7 @@ public static String getStackTraceString(Throwable e) {
         }
 
         StackTraceElement[] stacks = e.getStackTrace();
-        StringBuffer sb = new StringBuffer();
+        StringBuilder sb = new StringBuilder();
         for (StackTraceElement stack : stacks) {
             sb.append(stack.toString()).append('\n');
         }
@@ -1435,7 +1435,7 @@ public String getPrefix(String namespaceURI) {
         }
 
         @Override
-        public Iterator getPrefixes(String namespaceURI) {
+        public Iterator<String> getPrefixes(String namespaceURI) {
             return null;
         }
     }
diff --git a/impl/src/main/java/com/sun/faces/vendor/WebContainerInjectionProvider.java b/impl/src/main/java/com/sun/faces/vendor/WebContainerInjectionProvider.java
index aa563c211c..68e9c88951 100644
--- a/impl/src/main/java/com/sun/faces/vendor/WebContainerInjectionProvider.java
+++ b/impl/src/main/java/com/sun/faces/vendor/WebContainerInjectionProvider.java
@@ -47,7 +47,7 @@ public class WebContainerInjectionProvider implements InjectionProvider {
 
     private static final Logger LOGGER = FacesLogger.APPLICATION.getLogger();
 
-    private static Map<Class<?>, ConcurrentHashMap<Class<? extends Annotation>, MethodHolder>> methodsPerClazz = new ConcurrentHashMap<>();
+    private static final Map<Class<?>, ConcurrentHashMap<Class<? extends Annotation>, MethodHolder>> methodsPerClazz = new ConcurrentHashMap<>();
 
     // ------------------------------------------ Methods from InjectionProvider
 
@@ -74,7 +74,7 @@ public void invokePostConstruct(Object managedBean) throws InjectionProviderExce
 
     private static void invokeAnnotatedMethod(Method method, Object managedBean) throws InjectionProviderException {
         if (method != null) {
-            boolean accessible = method.isAccessible();
+            boolean accessible = method.canAccess(managedBean);
             method.setAccessible(true);
 
             try {
diff --git a/impl/src/main/java/jakarta/faces/annotation/ApplicationMap.java b/impl/src/main/java/jakarta/faces/annotation/ApplicationMap.java
index 753da6d89f..d384ce5df0 100644
--- a/impl/src/main/java/jakarta/faces/annotation/ApplicationMap.java
+++ b/impl/src/main/java/jakarta/faces/annotation/ApplicationMap.java
@@ -49,7 +49,7 @@
      *
      * @since 4.0
      */
-    public static final class Literal extends AnnotationLiteral<ApplicationMap> implements ApplicationMap {
+    final class Literal extends AnnotationLiteral<ApplicationMap> implements ApplicationMap {
         private static final long serialVersionUID = 1L;
 
         /**
diff --git a/impl/src/main/java/jakarta/faces/application/Application.java b/impl/src/main/java/jakarta/faces/application/Application.java
index 3a0484ffc5..0961525c58 100644
--- a/impl/src/main/java/jakarta/faces/application/Application.java
+++ b/impl/src/main/java/jakarta/faces/application/Application.java
@@ -941,7 +941,7 @@ public UIComponent createComponent(FacesContext context, Resource componentResou
      * @throws FacesException if the {@link Converter} cannot be created
      * @throws NullPointerException if <code>converterId</code> is <code>null</code>
      */
-    public abstract Converter createConverter(String converterId);
+    public abstract <T> Converter<T> createConverter(String converterId);
 
     /**
      * <p>
@@ -982,7 +982,7 @@ public UIComponent createComponent(FacesContext context, Resource componentResou
      * @throws FacesException if the {@link Converter} cannot be created
      * @throws NullPointerException if <code>targetClass</code> is <code>null</code>
      */
-    public abstract Converter createConverter(Class<?> targetClass);
+    public abstract <T> Converter<T> createConverter(Class<T> targetClass);
 
     /**
      * <p>
@@ -1224,7 +1224,7 @@ public ELContextListener[] getELContextListeners() {
      * @throws FacesException if a {@link Validator} of the specified id cannot be created
      * @throws NullPointerException if <code>validatorId</code> is <code>null</code>
      */
-    public abstract Validator createValidator(String validatorId) throws FacesException;
+    public abstract <T> Validator<T> createValidator(String validatorId) throws FacesException;
 
     /**
      * <p>
diff --git a/impl/src/main/java/jakarta/faces/application/ApplicationWrapper.java b/impl/src/main/java/jakarta/faces/application/ApplicationWrapper.java
index fa112728f2..fd08ac1488 100644
--- a/impl/src/main/java/jakarta/faces/application/ApplicationWrapper.java
+++ b/impl/src/main/java/jakarta/faces/application/ApplicationWrapper.java
@@ -331,7 +331,7 @@ public void addConverter(Class<?> targetClass, String converterClass) {
      * </p>
      */
     @Override
-    public Converter createConverter(String converterId) {
+    public <T> Converter<T> createConverter(String converterId) {
         return getWrapped().createConverter(converterId);
     }
 
@@ -342,7 +342,7 @@ public Converter createConverter(String converterId) {
      * </p>
      */
     @Override
-    public Converter createConverter(Class<?> targetClass) {
+    public <T> Converter<T> createConverter(Class<T> targetClass) {
         return getWrapped().createConverter(targetClass);
     }
 
diff --git a/impl/src/main/java/jakarta/faces/component/AttachedObjectListHolder.java b/impl/src/main/java/jakarta/faces/component/AttachedObjectListHolder.java
index c15d76fcac..bdf820302f 100644
--- a/impl/src/main/java/jakarta/faces/component/AttachedObjectListHolder.java
+++ b/impl/src/main/java/jakarta/faces/component/AttachedObjectListHolder.java
@@ -22,6 +22,7 @@
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Objects;
 
 import jakarta.faces.context.FacesContext;
 
@@ -76,10 +77,7 @@ public void clearInitialState() {
 
     @Override
     public Object saveState(FacesContext context) {
-
-        if (context == null) {
-            throw new NullPointerException();
-        }
+        Objects.requireNonNull(context);
 
         if (attachedObjects == null) {
             return null;
@@ -114,10 +112,7 @@ public Object saveState(FacesContext context) {
 
     @Override
     public void restoreState(FacesContext context, Object state) {
-
-        if (context == null) {
-            throw new NullPointerException();
-        }
+        Objects.requireNonNull(context);
 
         if (state == null) {
             return;
@@ -133,8 +128,8 @@ public void restoreState(FacesContext context, Object state) {
                 this.attachedObjects = new ArrayList<>(2);
             }
 
-            for (int i = 0, len = attachedObjects.length; i < len; i++) {
-                T restored = (T) ((StateHolderSaver) attachedObjects[i]).restore(context);
+            for (Object attachedObject : attachedObjects) {
+                T restored = (T) ((StateHolderSaver) attachedObject).restore(context);
                 if (restored != null) {
                     add(restored);
                 }
diff --git a/impl/src/main/java/jakarta/faces/component/EditableValueHolder.java b/impl/src/main/java/jakarta/faces/component/EditableValueHolder.java
index 5253c27b15..c4cd72be27 100644
--- a/impl/src/main/java/jakarta/faces/component/EditableValueHolder.java
+++ b/impl/src/main/java/jakarta/faces/component/EditableValueHolder.java
@@ -145,7 +145,7 @@ public interface EditableValueHolder extends ValueHolder {
      *
      * @throws NullPointerException if <code>validator</code> is null
      */
-    void addValidator(Validator validator);
+    void addValidator(Validator<?> validator);
 
     /**
      * <p>
@@ -155,7 +155,7 @@ public interface EditableValueHolder extends ValueHolder {
      *
      * @return the validators, or a zero-length array.
      */
-    Validator[] getValidators();
+    Validator<?>[] getValidators();
 
     /**
      * <p>
@@ -165,7 +165,7 @@ public interface EditableValueHolder extends ValueHolder {
      *
      * @param validator The {@link Validator} to remove
      */
-    void removeValidator(Validator validator);
+    void removeValidator(Validator<?> validator);
 
     /**
      * <p>
diff --git a/impl/src/main/java/jakarta/faces/component/MessageFactory.java b/impl/src/main/java/jakarta/faces/component/MessageFactory.java
index 367ce62fc7..cc14e00c7b 100644
--- a/impl/src/main/java/jakarta/faces/component/MessageFactory.java
+++ b/impl/src/main/java/jakarta/faces/component/MessageFactory.java
@@ -307,7 +307,7 @@ private String getFormattedString(String msgtext, Object[] params) {
             if (params == null || msgtext == null) {
                 return msgtext;
             }
-            StringBuffer b = new StringBuffer(100);
+            StringBuilder b = new StringBuilder(100);
             MessageFormat mf = new MessageFormat(msgtext);
             if (locale != null) {
                 mf.setLocale(locale);
@@ -317,8 +317,8 @@ private String getFormattedString(String msgtext, Object[] params) {
             return localizedStr;
         }
 
-        private Locale locale;
-        private Object[] parameters;
+        private final Locale locale;
+        private final Object[] parameters;
         private Object[] resolvedParameters;
     }
 
diff --git a/impl/src/main/java/jakarta/faces/component/SelectItemsIterator.java b/impl/src/main/java/jakarta/faces/component/SelectItemsIterator.java
index 47ba51c16f..aaddfccb28 100644
--- a/impl/src/main/java/jakarta/faces/component/SelectItemsIterator.java
+++ b/impl/src/main/java/jakarta/faces/component/SelectItemsIterator.java
@@ -70,7 +70,7 @@ public SelectItemsIterator(FacesContext ctx, UIComponent parent) {
      * Iterator over the children of the parent component.
      * </p>
      */
-    private ListIterator<UIComponent> kids;
+    private final ListIterator<UIComponent> kids;
 
     /**
      * Expose single SelectItems via an Iterator. This iterator will be reset/reused for each individual SelectItem instance
@@ -81,7 +81,7 @@ public SelectItemsIterator(FacesContext ctx, UIComponent parent) {
     /**
      * The {@link FacesContext} for the current request.
      */
-    private FacesContext ctx;
+    private final FacesContext ctx;
 
     // -------------------------------------------------------- Iterator Methods
 
@@ -274,12 +274,12 @@ private void updateItem(SelectItem item) {
      */
     private static final class MapIterator implements Iterator<SelectItem> {
 
-        private SelectItem item = new SelectItem();
-        private Iterator iterator;
+        private final SelectItem item = new SelectItem();
+        private final Iterator<? extends Map.Entry<?, ?>> iterator;
 
         // -------------------------------------------------------- Constructors
 
-        private MapIterator(Map map) {
+        private MapIterator(Map<?,?> map) {
 
             iterator = map.entrySet().iterator();
 
@@ -297,7 +297,7 @@ public boolean hasNext() {
         @Override
         public SelectItem next() {
 
-            Map.Entry entry = (Map.Entry) iterator.next();
+            Map.Entry<?,?> entry = iterator.next();
             Object key = entry.getKey();
             Object value = entry.getValue();
             item.setLabel(key != null ? key.toString() : value.toString());
@@ -403,9 +403,9 @@ private static final class GenericObjectSelectItem extends SelectItem {
             /**
              * The request-scoped variable under which the current object will be exposed.
              */
-            private String var;
+            private final String var;
 
-            private UISelectItems sourceComponent;
+            private final UISelectItems sourceComponent;
 
             // -------------------------------------------------------- Constructors
 
@@ -448,9 +448,9 @@ private void updateItem(FacesContext ctx, Object value) {
                     setValue(itemValueResult != null ? itemValueResult : value);
                     setLabel(itemLabelResult != null ? itemLabelResult.toString() : value.toString());
                     setDescription(itemDescriptionResult != null ? itemDescriptionResult.toString() : null);
-                    setEscape(itemEscapedResult != null ? Boolean.valueOf(itemEscapedResult.toString()) : true);
-                    setDisabled(itemDisabledResult != null ? Boolean.valueOf(itemDisabledResult.toString()) : false);
-                    setNoSelectionOption(noSelectionOptionResult != null ? Boolean.valueOf(noSelectionOptionResult.toString()) : false);
+                    setEscape(itemEscapedResult == null || Boolean.parseBoolean(itemEscapedResult.toString()));
+                    setDisabled(itemDisabledResult != null && Boolean.parseBoolean(itemDisabledResult.toString()));
+                    setNoSelectionOption(noSelectionOptionResult != null && Boolean.parseBoolean(noSelectionOptionResult.toString()));
                 } finally {
                     if (var != null) {
                         if (oldVarValue != null) {
@@ -489,9 +489,9 @@ private void readObject(ObjectInputStream in) throws IOException {
      */
     private static final class ArrayIterator extends GenericObjectSelectItemIterator {
 
-        private FacesContext ctx;
-        private Object array;
-        private int count;
+        private final FacesContext ctx;
+        private final Object array;
+        private final int count;
         private int index;
 
         // -------------------------------------------------------- Constructors
@@ -538,15 +538,15 @@ public void remove() {
     } // END ArrayIterator
 
     /**
-     * Handles Collections of <code>SelectItem</code>s, generic Objects, or combintations of both.
+     * Handles Collections of <code>SelectItem</code>s, generic Objects, or combinations of both.
      *
      * A single <code>GenericObjectSelectItem</code> will be leverage for any non-<code>SelectItem</code> objects
      * encountered.
      */
     private static final class IterableItemIterator extends GenericObjectSelectItemIterator {
 
-        private FacesContext ctx;
-        private Iterator<?> iterator;
+        private final FacesContext ctx;
+        private final Iterator<?> iterator;
 
         // -------------------------------------------------------- Constructors
 
diff --git a/impl/src/main/java/jakarta/faces/component/SelectUtils.java b/impl/src/main/java/jakarta/faces/component/SelectUtils.java
index 4850650540..83d9b5c8c8 100644
--- a/impl/src/main/java/jakarta/faces/component/SelectUtils.java
+++ b/impl/src/main/java/jakarta/faces/component/SelectUtils.java
@@ -49,14 +49,14 @@ private SelectUtils() {
      * @param items Iterator over the {@link jakarta.faces.model.SelectItem}s to be checked
      * @param converter the {@link Converter} associated with this component
      */
-    static boolean matchValue(FacesContext ctx, UIComponent component, Object value, Iterator<SelectItem> items, Converter converter) {
+    static boolean matchValue(FacesContext ctx, UIComponent component, Object value, Iterator<SelectItem> items, Converter<?> converter) {
 
         while (items.hasNext()) {
             SelectItem item = items.next();
             if (item instanceof SelectItemGroup) {
-                SelectItem subitems[] = ((SelectItemGroup) item).getSelectItems();
+                SelectItem[] subitems = ((SelectItemGroup) item).getSelectItems();
                 if (subitems != null && subitems.length > 0) {
-                    if (matchValue(ctx, component, value, new ArrayIterator(subitems), converter)) {
+                    if (matchValue(ctx, component, value, new ArrayIterator<>(subitems), converter)) {
                         return true;
                     }
                 }
@@ -92,15 +92,15 @@ static boolean matchValue(FacesContext ctx, UIComponent component, Object value,
      * @return
      */
 
-    static boolean valueIsNoSelectionOption(FacesContext ctx, UIComponent component, Object value, Iterator<SelectItem> items, Converter converter) {
+    static boolean valueIsNoSelectionOption(FacesContext ctx, UIComponent component, Object value, Iterator<SelectItem> items, Converter<?> converter) {
         boolean result = false;
 
         while (items.hasNext()) {
             SelectItem item = items.next();
             if (item instanceof SelectItemGroup) {
-                SelectItem subitems[] = ((SelectItemGroup) item).getSelectItems();
+                SelectItem[] subitems = ((SelectItemGroup) item).getSelectItems();
                 if (subitems != null && subitems.length > 0) {
-                    if (valueIsNoSelectionOption(ctx, component, value, new ArrayIterator(subitems), converter)) {
+                    if (valueIsNoSelectionOption(ctx, component, value, new ArrayIterator<>(subitems), converter)) {
                         result = true;
                         break;
                     }
@@ -128,7 +128,7 @@ static boolean valueIsNoSelectionOption(FacesContext ctx, UIComponent component,
         return result;
     }
 
-    private static Object doConversion(FacesContext ctx, UIComponent component, SelectItem item, Object value, Converter converter)
+    private static Object doConversion(FacesContext ctx, UIComponent component, SelectItem item, Object value, Converter<?> converter)
             throws IllegalStateException {
         Object itemValue = item.getValue();
         if (itemValue == null && value == null) {
@@ -159,7 +159,7 @@ private static Object doConversion(FacesContext ctx, UIComponent component, Sele
      * @param value the value to coerce
      * @param toType the type <code>value</code> should be coerced to
      *
-     * @return the result of the Jakarta Expression Language coersion
+     * @return the result of the Jakarta Expression Language coercion
      *
      * @see ExpressionFactory#coerceToType(Object, Class)
      */
@@ -185,13 +185,13 @@ private static Object coerceToModelType(FacesContext ctx, Object value, Class<?>
     /**
      * Exposes an Array via an <code>Iterator</code>
      */
-    static class ArrayIterator implements Iterator {
+    static class ArrayIterator<T> implements Iterator<T> {
 
-        public ArrayIterator(Object items[]) {
+        public ArrayIterator(T[] items) {
             this.items = items;
         }
 
-        private Object items[];
+        private final T[] items;
         private int index = 0;
 
         @Override
@@ -200,7 +200,7 @@ public boolean hasNext() {
         }
 
         @Override
-        public Object next() {
+        public T next() {
             try {
                 return items[index++];
             } catch (IndexOutOfBoundsException e) {
diff --git a/impl/src/main/java/jakarta/faces/component/UIComponent.java b/impl/src/main/java/jakarta/faces/component/UIComponent.java
index 73ca46a156..f6dbb58997 100644
--- a/impl/src/main/java/jakarta/faces/component/UIComponent.java
+++ b/impl/src/main/java/jakarta/faces/component/UIComponent.java
@@ -312,10 +312,7 @@ public Map<String, Object> getPassThroughAttributes(boolean create) {
      *
      */
     public ValueExpression getValueExpression(String name) {
-
-        if (name == null) {
-            throw new NullPointerException();
-        }
+        Objects.requireNonNull(name);
 
         @SuppressWarnings("unchecked")
         Map<String, ValueExpression> map = (Map<String, ValueExpression>) getStateHelper().get(UIComponentBase.PropertyKeys.bindings);
@@ -1572,9 +1569,9 @@ public static boolean isCompositeComponent(UIComponent component) {
         if (component == null) {
             throw new NullPointerException();
         }
-        boolean result = false;
+        boolean result;
         if (null != component.isCompositeComponent) {
-            result = component.isCompositeComponent.booleanValue();
+            result = component.isCompositeComponent;
         } else {
             result = component.isCompositeComponent = component.getAttributes().containsKey(Resource.COMPONENT_RESOURCE_KEY);
         }
@@ -1705,7 +1702,7 @@ public static UIComponent getCurrentCompositeComponent(FacesContext context) {
      * @throws IllegalArgumentException if <code>class</code> is not, and does not implement, {@link FacesListener}
      * @throws NullPointerException if <code>clazz</code> is <code>null</code>
      */
-    protected abstract FacesListener[] getFacesListeners(Class clazz);
+    protected abstract FacesListener[] getFacesListeners(Class<?> clazz);
 
     /**
      * <p>
@@ -1980,11 +1977,10 @@ public void processEvent(ComponentSystemEvent event) throws AbortProcessingExcep
      * Convenience method to return the {@link Renderer} instance associated with this component, if any; otherwise, return
      * <code>null</code>.
      * </p>
-     *
      * @param context {@link FacesContext} for the current request
      * @return the renderer, or <code>null</code>.
      */
-    protected abstract Renderer getRenderer(FacesContext context);
+    protected abstract Renderer<? extends UIComponent> getRenderer(FacesContext context);
 
     // --------------------------------------------------------- Package Private
 
diff --git a/impl/src/main/java/jakarta/faces/component/UIComponentBase.java b/impl/src/main/java/jakarta/faces/component/UIComponentBase.java
index 8ccbfee967..4ab9391ef1 100644
--- a/impl/src/main/java/jakarta/faces/component/UIComponentBase.java
+++ b/impl/src/main/java/jakarta/faces/component/UIComponentBase.java
@@ -42,20 +42,8 @@
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
-import java.util.AbstractCollection;
-import java.util.AbstractMap;
-import java.util.AbstractSet;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.List;
-import java.util.ListIterator;
-import java.util.Map;
+import java.util.*;
 import java.util.Map.Entry;
-import java.util.NoSuchElementException;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.logging.Level;
@@ -652,7 +640,7 @@ protected void addFacesListener(FacesListener listener) {
      * @throws NullPointerException {@inheritDoc}
      */
     @Override
-    protected FacesListener[] getFacesListeners(Class clazz) {
+    protected FacesListener[] getFacesListeners(Class<?> clazz) {
 
         if (clazz == null) {
             throw new NullPointerException();
@@ -672,7 +660,7 @@ protected FacesListener[] getFacesListeners(Class clazz) {
 
         List<FacesListener> results = new ArrayList<>(listeners.length);
         for (FacesListener listener : listeners) {
-            if (((Class<?>) clazz).isAssignableFrom(listener.getClass())) {
+            if (clazz.isAssignableFrom(listener.getClass())) {
                 results.add(listener);
             }
         }
@@ -763,11 +751,7 @@ public void subscribeToEvent(Class<? extends SystemEvent> eventClass, ComponentS
         }
 
         SystemEventListener facesLifecycleListener = new ComponentSystemEventListenerAdapter(componentListener, this);
-        List<SystemEventListener> listenersForEventClass = listenersByEventClass.get(eventClass);
-        if (listenersForEventClass == null) {
-            listenersForEventClass = new ArrayList<>(3);
-            listenersByEventClass.put(eventClass, listenersForEventClass);
-        }
+        List<SystemEventListener> listenersForEventClass = listenersByEventClass.computeIfAbsent(eventClass, k -> new ArrayList<>(3));
 
         if (!listenersForEventClass.contains(facesLifecycleListener)) {
             listenersForEventClass.add(facesLifecycleListener);
@@ -1038,9 +1022,9 @@ protected FacesContext getFacesContext() {
     }
 
     @Override
-    protected Renderer getRenderer(FacesContext context) {
+    protected Renderer<? extends UIComponent> getRenderer(FacesContext context) {
 
-        Renderer renderer = null;
+        Renderer<? extends UIComponent> renderer = null;
 
         String rendererType = getRendererType();
         if (rendererType != null) {
@@ -1052,7 +1036,7 @@ protected Renderer getRenderer(FacesContext context) {
         } else {
             if (LOGGER.isLoggable(FINE)) {
                 String id = getId();
-                LOGGER.fine("No renderer-type for component " + id != null ? id : getClass().getName());
+                LOGGER.fine("No renderer-type for component " + (id != null ? id : getClass().getName()) );
             }
         }
 
@@ -1272,9 +1256,7 @@ public void setTransient(boolean transientFlag) {
      */
 
     public static Object saveAttachedState(FacesContext context, Object attachedObject) {
-        if (context == null) {
-            throw new NullPointerException();
-        }
+        Objects.requireNonNull(context);
 
         if (attachedObject == null) {
             return null;
@@ -1295,7 +1277,7 @@ public static Object saveAttachedState(FacesContext context, Object attachedObje
         }
 
         if (newWillSucceed && attachedObject instanceof Collection) {
-            Collection attachedCollection = (Collection) attachedObject;
+            Collection<?> attachedCollection = (Collection<?>) attachedObject;
             List<StateHolderSaver> resultList = new ArrayList<>(attachedCollection.size() + 1);
             resultList.add(new StateHolderSaver(context, mapOrCollectionClass));
             for (Object item : attachedCollection) {
diff --git a/impl/src/main/java/jakarta/faces/component/UIInput.java b/impl/src/main/java/jakarta/faces/component/UIInput.java
index ad8ad72001..4c3a1bb0b3 100644
--- a/impl/src/main/java/jakarta/faces/component/UIInput.java
+++ b/impl/src/main/java/jakarta/faces/component/UIInput.java
@@ -16,10 +16,7 @@
 
 package jakarta.faces.component;
 
-import java.util.Collection;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 import jakarta.el.ELException;
 import jakarta.el.ValueExpression;
@@ -155,7 +152,7 @@ public class UIInput extends UIOutput implements EditableValueHolder {
      */
     public static final String ALWAYS_PERFORM_VALIDATION_WHEN_REQUIRED_IS_TRUE = "jakarta.faces.ALWAYS_PERFORM_VALIDATION_WHEN_REQUIRED_IS_TRUE";
 
-    private static final Validator[] EMPTY_VALIDATOR = new Validator[0];
+    private static final Validator<?>[] EMPTY_VALIDATOR = new Validator[0];
 
     private transient Boolean emptyStringIsNull;
 
@@ -1124,21 +1121,12 @@ public static boolean isEmpty(Object value) {
         } else if (value instanceof String && ((String) value).length() < 1) {
             return true;
         } else if (value.getClass().isArray()) {
-            if (0 == java.lang.reflect.Array.getLength(value)) {
-                return true;
-            }
+            return 0 == java.lang.reflect.Array.getLength(value);
         } else if (value instanceof List) {
-            if (((List) value).isEmpty()) {
-                return true;
-            }
+            return ((List) value).isEmpty();
         } else if (value instanceof Collection) {
-            if (((Collection) value).isEmpty()) {
-                return true;
-            }
-        } else if (value instanceof Map && ((Map) value).isEmpty()) {
-            return true;
-        }
-        return false;
+            return ((Collection) value).isEmpty();
+        } else return value instanceof Map && ((Map) value).isEmpty();
     }
 
     /**
@@ -1157,11 +1145,8 @@ public static boolean isEmpty(Object value) {
      * @throws NullPointerException if <code>validator</code> is null
      */
     @Override
-    public void addValidator(Validator validator) {
-
-        if (validator == null) {
-            throw new NullPointerException();
-        }
+    public void addValidator(Validator<?> validator) {
+        Objects.requireNonNull(validator);
 
         if (validators == null) {
             validators = new AttachedObjectListHolder<>();
@@ -1177,7 +1162,7 @@ public void addValidator(Validator validator) {
      * </p>
      */
     @Override
-    public Validator[] getValidators() {
+    public Validator<?>[] getValidators() {
 
         return validators != null ? validators.asArray(Validator.class) : EMPTY_VALIDATOR;
 
@@ -1192,7 +1177,7 @@ public Validator[] getValidators() {
      * @param validator The {@link Validator} to remove
      */
     @Override
-    public void removeValidator(Validator validator) {
+    public void removeValidator(Validator<?> validator) {
 
         if (validator == null) {
             return;
@@ -1291,8 +1276,8 @@ public void restoreState(FacesContext context, Object state) {
 
     }
 
-    private Converter getConverterWithType(FacesContext context) {
-        Converter converter = getConverter();
+    private Converter<?> getConverterWithType(FacesContext context) {
+        Converter<?> converter = getConverter();
         if (converter != null) {
             return converter;
         }
diff --git a/impl/src/main/java/jakarta/faces/component/UIOutput.java b/impl/src/main/java/jakarta/faces/component/UIOutput.java
index bb5be933bd..5fd4212465 100644
--- a/impl/src/main/java/jakarta/faces/component/UIOutput.java
+++ b/impl/src/main/java/jakarta/faces/component/UIOutput.java
@@ -19,6 +19,8 @@
 import jakarta.faces.context.FacesContext;
 import jakarta.faces.convert.Converter;
 
+import java.util.Objects;
+
 /**
  * <p>
  * <strong class="changed_modified_2_0_rev_a changed_modified_2_2">UIOutput</strong> is a {@link UIComponent} that has a
@@ -98,17 +100,17 @@ public String getFamily() {
     // --------------------------------------- EditableValueHolder Properties
 
     @Override
-    public Converter getConverter() {
+    public Converter<?> getConverter() {
 
         if (converter != null) {
             return converter;
         }
 
-        return (Converter) getStateHelper().eval(PropertyKeys.converter);
+        return (Converter<?>) getStateHelper().eval(PropertyKeys.converter);
     }
 
     @Override
-    public void setConverter(Converter converter) {
+    public void setConverter(Converter<?> converter) {
 
         clearInitialState();
         // we don't push the converter to the StateHelper
@@ -173,7 +175,7 @@ public void clearInitialState() {
             super.clearInitialState();
 
             Converter<?> c = getConverter();
-            if (c != null && c instanceof PartialStateHolder) {
+            if (c instanceof PartialStateHolder) {
                 ((PartialStateHolder) c).clearInitialState();
             }
         }
@@ -181,9 +183,7 @@ public void clearInitialState() {
 
     @Override
     public Object saveState(FacesContext context) {
-        if (context == null) {
-            throw new NullPointerException();
-        }
+        Objects.requireNonNull(context);
 
         Object converterState = null;
         if (converter != null) {
@@ -222,10 +222,7 @@ public Object saveState(FacesContext context) {
 
     @Override
     public void restoreState(FacesContext context, Object state) {
-
-        if (context == null) {
-            throw new NullPointerException();
-        }
+        Objects.requireNonNull(context);
 
         if (state == null) {
             return;
diff --git a/impl/src/main/java/jakarta/faces/component/UISelectMany.java b/impl/src/main/java/jakarta/faces/component/UISelectMany.java
index 046e1c1baf..b4e7fcea4c 100644
--- a/impl/src/main/java/jakarta/faces/component/UISelectMany.java
+++ b/impl/src/main/java/jakarta/faces/component/UISelectMany.java
@@ -18,14 +18,17 @@
 package jakarta.faces.component;
 
 import java.lang.reflect.Array;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
+import java.util.stream.IntStream;
 
 import jakarta.el.ValueExpression;
 import jakarta.faces.application.FacesMessage;
 import jakarta.faces.context.FacesContext;
 import jakarta.faces.convert.Converter;
+import jakarta.faces.model.SelectItem;
 
 /**
  * <p>
@@ -413,9 +416,9 @@ protected boolean compareValues(Object previous, Object value) {
         // it will not suffice to just compare the element position and position.
         int count1;
         int count2;
-        for (int i = 0; i < oldarray.length; ++i) {
-            count1 = countElementOccurrence(oldarray[i], oldarray);
-            count2 = countElementOccurrence(oldarray[i], newarray);
+        for (Object oldElement : oldarray) {
+            count1 = countElementOccurrence(oldElement, oldarray);
+            count2 = countElementOccurrence(oldElement, newarray);
             if (count1 != count2) {
                 valueChanged = true;
                 break;
@@ -435,8 +438,7 @@ protected boolean compareValues(Object previous, Object value) {
      */
     private static int countElementOccurrence(Object element, Object[] array) {
         int count = 0;
-        for (int i = 0; i < array.length; ++i) {
-            Object arrayElement = array[i];
+        for (Object arrayElement : array) {
             if (arrayElement != null && element != null) {
                 if (arrayElement.equals(element)) {
                     count++;
@@ -523,9 +525,9 @@ protected void validateValue(FacesContext context, Object value) {
         // Ensure that the values match one of the available options
         // Don't arrays cast to "Object[]", as we may now be using an array
         // of primitives
-        Converter converter = getConverter();
-        for (Iterator i = getValuesIterator(value); i.hasNext();) {
-            Iterator items = new SelectItemsIterator(context, this);
+        Converter<?> converter = getConverter();
+        for (Iterator<?> i = getValuesIterator(value); i.hasNext();) {
+            Iterator<SelectItem> items = new SelectItemsIterator(context, this);
             Object currentValue = i.next();
             if (!SelectUtils.matchValue(context, this, currentValue, items, converter)) {
                 doAddMessage = true;
@@ -536,8 +538,8 @@ protected void validateValue(FacesContext context, Object value) {
         // Ensure that if the value is noSelection and a
         // value is required, a message is queued
         if (isRequired()) {
-            for (Iterator i = getValuesIterator(value); i.hasNext();) {
-                Iterator items = new SelectItemsIterator(context, this);
+            for (Iterator<?> i = getValuesIterator(value); i.hasNext();) {
+                Iterator<SelectItem> items = new SelectItemsIterator(context, this);
                 Object currentValue = i.next();
                 if (SelectUtils.valueIsNoSelectionOption(context, this, currentValue, items, converter)) {
                     doAddMessage = true;
@@ -557,12 +559,12 @@ protected void validateValue(FacesContext context, Object value) {
 
     // --------------------------------------------------------- Private Methods
 
-    private Iterator getValuesIterator(Object value) {
+    private <T> Iterator<T> getValuesIterator(Object value) {
         if (value instanceof Collection) {
-            return ((Collection) value).iterator();
+            return ((Collection<T>) value).iterator();
         }
 
-        return new ArrayIterator(value);
+        return new ArrayIterator<>(value);
     }
 
     // ---------------------------------------------------------- Nested Classes
@@ -570,19 +572,17 @@ private Iterator getValuesIterator(Object value) {
     /**
      * Exposes an Array as an Iterator.
      */
-    private static final class ArrayIterator implements Iterator {
+    private static final class ArrayIterator<T> implements Iterator<T> {
 
-        private int length;
+        private final int length;
         private int idx = 0;
-        private Object value;
+        private final Object value;
 
         // -------------------------------------------------------- Constructors
 
         ArrayIterator(Object value) {
-
             this.value = value;
             length = Array.getLength(value);
-
         }
 
         // ------------------------------------------------------------ Iterator
@@ -593,21 +593,18 @@ public boolean hasNext() {
         }
 
         @Override
-        public Object next() {
-
+        @SuppressWarnings("unchecked")
+        public T next() {
             if (idx >= length) {
                 throw new NoSuchElementException();
             } else {
-                return Array.get(value, idx++);
+                return (T)Array.get(value, idx++);
             }
-
         }
 
         @Override
         public void remove() {
-
             throw new UnsupportedOperationException();
-
         }
 
     }
diff --git a/impl/src/main/java/jakarta/faces/component/ValueHolder.java b/impl/src/main/java/jakarta/faces/component/ValueHolder.java
index 254801c2dc..d180e607d6 100644
--- a/impl/src/main/java/jakarta/faces/component/ValueHolder.java
+++ b/impl/src/main/java/jakarta/faces/component/ValueHolder.java
@@ -68,7 +68,7 @@ public interface ValueHolder {
      *
      * @return the converter.
      */
-    Converter getConverter();
+    Converter<?> getConverter();
 
     /**
      * <p>
@@ -77,5 +77,5 @@ public interface ValueHolder {
      *
      * @param converter New {@link Converter} (or <code>null</code>)
      */
-    void setConverter(Converter converter);
+    void setConverter(Converter<?> converter);
 }
diff --git a/impl/src/main/java/jakarta/faces/convert/MessageFactory.java b/impl/src/main/java/jakarta/faces/convert/MessageFactory.java
index 757a946022..1d4e33c7fc 100644
--- a/impl/src/main/java/jakarta/faces/convert/MessageFactory.java
+++ b/impl/src/main/java/jakarta/faces/convert/MessageFactory.java
@@ -309,7 +309,7 @@ private String getFormattedString(String msgtext, Object[] params) {
             if (params == null || msgtext == null) {
                 return msgtext;
             }
-            StringBuffer b = new StringBuffer(100);
+            StringBuilder b = new StringBuilder(100);
             MessageFormat mf = new MessageFormat(msgtext);
             if (locale != null) {
                 mf.setLocale(locale);
@@ -319,8 +319,8 @@ private String getFormattedString(String msgtext, Object[] params) {
             return localizedStr;
         }
 
-        private Locale locale;
-        private Object[] parameters;
+        private final Locale locale;
+        private final Object[] parameters;
         private Object[] resolvedParameters;
     }
 
diff --git a/impl/src/main/java/jakarta/faces/render/RenderKit.java b/impl/src/main/java/jakarta/faces/render/RenderKit.java
index 6f2e677e41..2686e8c5ab 100644
--- a/impl/src/main/java/jakarta/faces/render/RenderKit.java
+++ b/impl/src/main/java/jakarta/faces/render/RenderKit.java
@@ -20,7 +20,6 @@
 import java.io.Writer;
 import java.util.Collections;
 import java.util.Iterator;
-import java.util.Set;
 
 import jakarta.faces.component.UIComponent;
 import jakarta.faces.context.ResponseStream;
@@ -64,22 +63,19 @@ public abstract class RenderKit {
      *
      * @throws NullPointerException if <code>family</code> or <code>rendererType</code> or <code>renderer</code> is null
      */
-    public abstract void addRenderer(String family, String rendererType, Renderer renderer);
+    public abstract void addRenderer(String family, String rendererType, Renderer<? extends UIComponent> renderer);
 
     /**
      * <p>
      * Return the {@link Renderer} instance most recently registered for the specified component <code>family</code> and
      * <code>rendererType</code>, if any; otherwise, return <code>null</code>.
      * </p>
-     *
-     * @param family Component family of the requested {@link Renderer} instance
+     * @param family       Component family of the requested {@link Renderer} instance
      * @param rendererType Renderer type of the requested {@link Renderer} instance
-     *
-     * @throws NullPointerException if <code>family</code> or <code>rendererType</code> is <code>null</code>
-     *
      * @return the {@link Renderer} instance
+     * @throws NullPointerException if <code>family</code> or <code>rendererType</code> is <code>null</code>
      */
-    public abstract Renderer getRenderer(String family, String rendererType);
+    public abstract Renderer<? extends UIComponent> getRenderer(String family, String rendererType);
 
     /**
      * <p>
@@ -155,10 +151,7 @@ public abstract class RenderKit {
      *
      */
     public Iterator<String> getComponentFamilies() {
-
-        Set<String> empty = Collections.emptySet();
-        return empty.iterator();
-
+        return Collections.emptyIterator();
     }
 
     /**
@@ -183,10 +176,7 @@ public Iterator<String> getComponentFamilies() {
      *
      */
     public Iterator<String> getRendererTypes(String componentFamily) {
-
-        Set<String> empty = Collections.emptySet();
-        return empty.iterator();
-
+        return Collections.emptyIterator();
     }
 
     /**
diff --git a/impl/src/main/java/jakarta/faces/render/RenderKitWrapper.java b/impl/src/main/java/jakarta/faces/render/RenderKitWrapper.java
index 2187e52928..2e8ba0e955 100644
--- a/impl/src/main/java/jakarta/faces/render/RenderKitWrapper.java
+++ b/impl/src/main/java/jakarta/faces/render/RenderKitWrapper.java
@@ -21,6 +21,7 @@
 import java.util.Iterator;
 
 import jakarta.faces.FacesWrapper;
+import jakarta.faces.component.UIComponent;
 import jakarta.faces.context.ResponseStream;
 import jakarta.faces.context.ResponseWriter;
 
@@ -81,7 +82,7 @@ public RenderKit getWrapped() {
      * @see RenderKit#addRenderer(String, String, Renderer)
      */
     @Override
-    public void addRenderer(String family, String rendererType, Renderer renderer) {
+    public void addRenderer(String family, String rendererType, Renderer<? extends UIComponent> renderer) {
         getWrapped().addRenderer(family, rendererType, renderer);
     }
 
@@ -116,11 +117,10 @@ public ResponseWriter createResponseWriter(Writer writer, String contentTypeList
      * The default behavior of this method is to call {@link RenderKit#getRenderer(String, String)} on the wrapped
      * {@link RenderKit} object.
      * </p>
-     *
      * @see RenderKit#getRenderer(String, String)
      */
     @Override
-    public Renderer getRenderer(String family, String rendererType) {
+    public Renderer<? extends UIComponent> getRenderer(String family, String rendererType) {
         return getWrapped().getRenderer(family, rendererType);
     }
 
diff --git a/impl/src/main/java/jakarta/faces/render/Renderer.java b/impl/src/main/java/jakarta/faces/render/Renderer.java
index be48e83ef0..678c768beb 100644
--- a/impl/src/main/java/jakarta/faces/render/Renderer.java
+++ b/impl/src/main/java/jakarta/faces/render/Renderer.java
@@ -135,7 +135,7 @@ public void encodeBegin(FacesContext context, T component) throws IOException {
      * @throws IOException if an input/output error occurs while rendering
      * @throws NullPointerException if <code>context</code> or <code>component</code> is <code>null</code>
      */
-    public void encodeChildren(FacesContext context, T component) throws IOException {
+    public <T extends UIComponent> void encodeChildren(FacesContext context, T component) throws IOException {
         if (context == null || component == null) {
             throw new NullPointerException();
         }
diff --git a/impl/src/main/java/jakarta/faces/render/RendererWrapper.java b/impl/src/main/java/jakarta/faces/render/RendererWrapper.java
index 7043463880..8d863aa7e4 100644
--- a/impl/src/main/java/jakarta/faces/render/RendererWrapper.java
+++ b/impl/src/main/java/jakarta/faces/render/RendererWrapper.java
@@ -38,9 +38,9 @@
  * @since 2.2
  */
 
-public abstract class RendererWrapper extends Renderer implements FacesWrapper<Renderer> {
+public abstract class RendererWrapper<T extends UIComponent> extends Renderer<T> implements FacesWrapper<Renderer<T>> {
 
-    private Renderer wrapped;
+    private Renderer<T> wrapped;
 
     /**
      * @deprecated Use the other constructor taking the implementation being wrapped.
@@ -59,12 +59,12 @@ public RendererWrapper() {
      * @param wrapped The implementation being wrapped.
      * @since 2.3
      */
-    public RendererWrapper(Renderer wrapped) {
+    public RendererWrapper(Renderer<T> wrapped) {
         this.wrapped = wrapped;
     }
 
     @Override
-    public Renderer getWrapped() {
+    public Renderer<T> getWrapped() {
         return wrapped;
     }
 
@@ -79,22 +79,22 @@ public Object getConvertedValue(FacesContext context, UIComponent component, Obj
     }
 
     @Override
-    public void decode(FacesContext context, UIComponent component) {
+    public void decode(FacesContext context, T component) {
         getWrapped().decode(context, component);
     }
 
     @Override
-    public void encodeBegin(FacesContext context, UIComponent component) throws IOException {
+    public void encodeBegin(FacesContext context, T component) throws IOException {
         getWrapped().encodeBegin(context, component);
     }
 
     @Override
-    public void encodeChildren(FacesContext context, UIComponent component) throws IOException {
+    public <T extends UIComponent> void encodeChildren(FacesContext context, T component) throws IOException {
         getWrapped().encodeChildren(context, component);
     }
 
     @Override
-    public void encodeEnd(FacesContext context, UIComponent component) throws IOException {
+    public void encodeEnd(FacesContext context, T component) throws IOException {
         getWrapped().encodeEnd(context, component);
     }
 
diff --git a/impl/src/main/java/jakarta/faces/validator/DoubleRangeValidator.java b/impl/src/main/java/jakarta/faces/validator/DoubleRangeValidator.java
index 70c6a9478a..8708d92c6e 100644
--- a/impl/src/main/java/jakarta/faces/validator/DoubleRangeValidator.java
+++ b/impl/src/main/java/jakarta/faces/validator/DoubleRangeValidator.java
@@ -286,11 +286,10 @@ public boolean equals(Object otherObj) {
      */
     @Override
     public int hashCode() {
-
-        int hashCode = Double.valueOf(getMinimum()).hashCode() + Double.valueOf(getMaximum()).hashCode() + Boolean.valueOf(isMinimumSet()).hashCode()
-                + Boolean.valueOf(isMaximumSet()).hashCode();
-        return hashCode;
-
+        return  Double.hashCode(getMinimum()) +
+                Double.hashCode(getMaximum()) +
+                Boolean.hashCode(isMinimumSet()) +
+                Boolean.hashCode(isMaximumSet());
     }
 
     // --------------------------------------------------------- Private Methods
@@ -315,7 +314,7 @@ private static double doubleValue(Object attributeValue) throws NumberFormatExce
 
     private static String stringValue(UIComponent component, Double toConvert, FacesContext context) {
 
-        Converter converter = context.getApplication().createConverter("jakarta.faces.Number");
+        Converter<Number> converter = context.getApplication().createConverter("jakarta.faces.Number");
         return converter.getAsString(context, component, toConvert);
 
     }
@@ -341,7 +340,7 @@ public Object saveState(FacesContext context) {
             throw new NullPointerException();
         }
         if (!initialStateMarked()) {
-            Object values[] = new Object[2];
+            Object[] values = new Object[2];
             values[0] = maximum;
             values[1] = minimum;
             return values;
@@ -357,7 +356,7 @@ public void restoreState(FacesContext context, Object state) {
             throw new NullPointerException();
         }
         if (state != null) {
-            Object values[] = (Object[]) state;
+            Object[] values = (Object[]) state;
             maximum = (Double) values[0];
             minimum = (Double) values[1];
         }
diff --git a/impl/src/main/java/jakarta/faces/validator/MessageFactory.java b/impl/src/main/java/jakarta/faces/validator/MessageFactory.java
index 7a0083b00a..c971792bb9 100644
--- a/impl/src/main/java/jakarta/faces/validator/MessageFactory.java
+++ b/impl/src/main/java/jakarta/faces/validator/MessageFactory.java
@@ -309,7 +309,7 @@ private String getFormattedString(String msgtext, Object[] params) {
             if (params == null || msgtext == null) {
                 return msgtext;
             }
-            StringBuffer b = new StringBuffer(100);
+            StringBuilder b = new StringBuilder(100);
             MessageFormat mf = new MessageFormat(msgtext);
             if (locale != null) {
                 mf.setLocale(locale);
@@ -319,8 +319,8 @@ private String getFormattedString(String msgtext, Object[] params) {
             return localizedStr;
         }
 
-        private Locale locale;
-        private Object[] parameters;
+        private final Locale locale;
+        private final Object[] parameters;
         private Object[] resolvedParameters;
     }
 
diff --git a/impl/src/main/java/jakarta/faces/view/Location.java b/impl/src/main/java/jakarta/faces/view/Location.java
index 1991973578..a41a58e2fa 100644
--- a/impl/src/main/java/jakarta/faces/view/Location.java
+++ b/impl/src/main/java/jakarta/faces/view/Location.java
@@ -80,6 +80,6 @@ public String getPath() {
 
     @Override
     public String toString() {
-        return path + " @" + line + "," + column;
+        return path + ' ' + '@' + line + ',' + column;
     }
 }
diff --git a/impl/src/main/java/jakarta/faces/view/ViewMetadata.java b/impl/src/main/java/jakarta/faces/view/ViewMetadata.java
index 4b5e89f610..d96546b35f 100644
--- a/impl/src/main/java/jakarta/faces/view/ViewMetadata.java
+++ b/impl/src/main/java/jakarta/faces/view/ViewMetadata.java
@@ -134,7 +134,7 @@ public static boolean hasMetadata(UIViewRoot root) {
 
     @SuppressWarnings("unchecked")
     private static <C extends UIComponent> List<C> getMetadataChildren(UIViewRoot root, Class<C> type) {
-        return (List<C>) getMetadataFacet(root).map(m -> m.getChildren()).orElseGet(Collections::emptyList).stream().filter(c -> type.isInstance(c))
+        return (List<C>) getMetadataFacet(root).map(UIComponent::getChildren).orElseGet(Collections::emptyList).stream().filter(type::isInstance)
                 .collect(Collectors.toList());
     }
 
diff --git a/impl/src/main/java/jakarta/faces/view/facelets/FaceletCacheFactory.java b/impl/src/main/java/jakarta/faces/view/facelets/FaceletCacheFactory.java
index 37d31b1b5a..430ea97091 100644
--- a/impl/src/main/java/jakarta/faces/view/facelets/FaceletCacheFactory.java
+++ b/impl/src/main/java/jakarta/faces/view/facelets/FaceletCacheFactory.java
@@ -16,6 +16,7 @@
 
 package jakarta.faces.view.facelets;
 
+import com.sun.faces.facelets.impl.DefaultFaceletFactory;
 import jakarta.faces.FacesWrapper;
 
 /**
diff --git a/impl/src/main/java/jakarta/faces/view/facelets/Tag.java b/impl/src/main/java/jakarta/faces/view/facelets/Tag.java
index 2acc954b39..2d16b39390 100644
--- a/impl/src/main/java/jakarta/faces/view/facelets/Tag.java
+++ b/impl/src/main/java/jakarta/faces/view/facelets/Tag.java
@@ -143,6 +143,6 @@ public String getQName() {
      */
     @Override
     public String toString() {
-        return location + " <" + qName + ">";
+        return location + " <" + qName + '>';
     }
 }
diff --git a/impl/src/main/java/jakarta/faces/view/facelets/TagHandlerDelegate.java b/impl/src/main/java/jakarta/faces/view/facelets/TagHandlerDelegate.java
index bd1d30438e..0a077e2ddc 100644
--- a/impl/src/main/java/jakarta/faces/view/facelets/TagHandlerDelegate.java
+++ b/impl/src/main/java/jakarta/faces/view/facelets/TagHandlerDelegate.java
@@ -43,7 +43,7 @@ public abstract class TagHandlerDelegate {
      *
      * @since 2.0
      */
-    public abstract MetaRuleset createMetaRuleset(Class type);
+    public abstract MetaRuleset createMetaRuleset(Class<?> type);
 
     /**
      * <p class="changed_added_2_0">
diff --git a/impl/src/main/java/jakarta/faces/webapp/MessageFactory.java b/impl/src/main/java/jakarta/faces/webapp/MessageFactory.java
index 299bd1ed15..30a0764611 100644
--- a/impl/src/main/java/jakarta/faces/webapp/MessageFactory.java
+++ b/impl/src/main/java/jakarta/faces/webapp/MessageFactory.java
@@ -309,7 +309,7 @@ private String getFormattedString(String msgtext, Object[] params) {
             if (params == null || msgtext == null) {
                 return msgtext;
             }
-            StringBuffer b = new StringBuffer(100);
+            StringBuilder b = new StringBuilder(100);
             MessageFormat mf = new MessageFormat(msgtext);
             if (locale != null) {
                 mf.setLocale(locale);
@@ -319,8 +319,8 @@ private String getFormattedString(String msgtext, Object[] params) {
             return localizedStr;
         }
 
-        private Locale locale;
-        private Object[] parameters;
+        private final Locale locale;
+        private final Object[] parameters;
         private Object[] resolvedParameters;
     }
 
diff --git a/impl/src/test/java/com/sun/faces/mock/MockApplication.java b/impl/src/test/java/com/sun/faces/mock/MockApplication.java
index b1dcf084ff..d1fdfc00a7 100644
--- a/impl/src/test/java/com/sun/faces/mock/MockApplication.java
+++ b/impl/src/test/java/com/sun/faces/mock/MockApplication.java
@@ -203,7 +203,7 @@ public void setStateManager(StateManager stateManager) {
         this.stateManager = stateManager;
     }
 
-    private Map<String, String> components = new HashMap<>();
+    private final Map<String, String> components = new HashMap<>();
 
     @Override
     public void addComponent(String componentType, String componentClass) {
@@ -234,7 +234,7 @@ public Iterator<String> getComponentTypes() {
         return (components.keySet().iterator());
     }
 
-    private Map<String, String> converters = new HashMap<>();
+    private final Map<String, String> converters = new HashMap<>();
 
     @Override
     public void addConverter(String converterId, String converterClass) {
@@ -247,18 +247,18 @@ public void addConverter(Class<?> targetClass, String converterClass) {
     }
 
     @Override
-    public Converter createConverter(String converterId) {
+    public <T> Converter<T> createConverter(String converterId) {
         String converterClass = converters.get(converterId);
         try {
-            Class<?> clazz = Class.forName(converterClass);
-            return ((Converter) clazz.getDeclaredConstructor().newInstance());
+            Class<T> clazz = (Class<T>) Class.forName(converterClass);
+            return (Converter<T>) clazz.getDeclaredConstructor().newInstance();
         } catch (Exception e) {
             throw new FacesException(e);
         }
     }
 
     @Override
-    public Converter createConverter(Class<?> targetClass) {
+    public <T> Converter<T> createConverter(Class<T> targetClass) {
         throw new UnsupportedOperationException();
     }
 
@@ -284,7 +284,7 @@ public String getMessageBundle() {
         return messageBundle;
     }
 
-    private Map<String, String> validators = new HashMap<>();
+    private final Map<String, String> validators = new HashMap<>();
 
     @Override
     public void addValidator(String validatorId, String validatorClass) {
@@ -292,11 +292,11 @@ public void addValidator(String validatorId, String validatorClass) {
     }
 
     @Override
-    public Validator createValidator(String validatorId) {
+    public <T> Validator<T> createValidator(String validatorId) {
         String validatorClass = validators.get(validatorId);
         try {
-            Class<?> clazz = Class.forName(validatorClass);
-            return ((Validator) clazz.getDeclaredConstructor().newInstance());
+            Class<T> clazz = (Class<T>) Class.forName(validatorClass);
+            return ((Validator<T>) clazz.getDeclaredConstructor().newInstance());
         } catch (Exception e) {
             throw new FacesException(e);
         }
diff --git a/impl/src/test/java/com/sun/faces/mock/MockRenderKit.java b/impl/src/test/java/com/sun/faces/mock/MockRenderKit.java
index 8c2471b0c0..78814500c5 100644
--- a/impl/src/test/java/com/sun/faces/mock/MockRenderKit.java
+++ b/impl/src/test/java/com/sun/faces/mock/MockRenderKit.java
@@ -52,12 +52,11 @@ public MockRenderKit() {
         responseStateManager = new MockResponseStateManager();
     }
 
-    private Map<String, Renderer> renderers = new HashMap<>();
+    private final Map<String, Renderer<? extends UIComponent>> renderers = new HashMap<>();
     private ResponseStateManager responseStateManager = null;
 
     @Override
-    public void addRenderer(String family, String rendererType,
-            Renderer renderer) {
+    public void addRenderer(String family, String rendererType, Renderer<? extends UIComponent> renderer) {
         if ((family == null) || (rendererType == null) || (renderer == null)) {
             throw new NullPointerException();
         }
@@ -65,7 +64,7 @@ public void addRenderer(String family, String rendererType,
     }
 
     @Override
-    public Renderer getRenderer(String family, String rendererType) {
+    public Renderer<? extends UIComponent> getRenderer(String family, String rendererType) {
         if ((family == null) || (rendererType == null)) {
             throw new NullPointerException();
         }
@@ -115,7 +114,7 @@ public ResponseStateManager getResponseStateManager() {
         return responseStateManager;
     }
 
-    class TestRenderer extends Renderer<UIComponent> {
+    static class TestRenderer extends Renderer<UIComponent> {
 
         public TestRenderer() {
         }
@@ -163,12 +162,5 @@ public void encodeChildren(FacesContext context, UIComponent component)
             }
         }
 
-        @Override
-        public void encodeEnd(FacesContext context, UIComponent component)
-                throws IOException {
-            if ((context == null) || (component == null)) {
-                throw new NullPointerException();
-            }
-        }
     }
 }
diff --git a/impl/src/test/java/com/sun/faces/util/MostlySingletonTest.java b/impl/src/test/java/com/sun/faces/util/MostlySingletonTest.java
index 26ead141bf..3c08ffd841 100644
--- a/impl/src/test/java/com/sun/faces/util/MostlySingletonTest.java
+++ b/impl/src/test/java/com/sun/faces/util/MostlySingletonTest.java
@@ -28,7 +28,7 @@ public MostlySingletonTest() {
     
     @Test
     public void testAdd() {
-        MostlySingletonSet<Integer> set = new MostlySingletonSet<Integer>();
+        MostlySingletonSet<Integer> set = new MostlySingletonSet<>();
         
         set.add(1);
         assertTrue(1 == set.size());
@@ -60,12 +60,12 @@ public void testAddWithNulls() {
     
     @Test
     public void testAddAll() {
-        Set<Integer> otherSet = new HashSet<Integer>();
+        Set<Integer> otherSet = new HashSet<>();
         otherSet.add(4);
         otherSet.add(5);
         otherSet.add(6);
         
-        MostlySingletonSet<Integer> set = new MostlySingletonSet<Integer>();
+        MostlySingletonSet<Integer> set = new MostlySingletonSet<>();
         
         set.add(1);
         assertTrue(1 == set.size());
@@ -112,7 +112,7 @@ public void testAddAll() {
     
     @Test
     public void testRemove() {
-        MostlySingletonSet<Integer> set = new MostlySingletonSet<Integer>();
+        MostlySingletonSet<Integer> set = new MostlySingletonSet<>();
         
         set.add(1);
         assertTrue(1 == set.size());
@@ -154,7 +154,7 @@ public void testRemove() {
     
     @Test
     public void testRemoveWithNulls() {
-        MostlySingletonSet<Integer> set = new MostlySingletonSet<Integer>();
+        MostlySingletonSet<Integer> set = new MostlySingletonSet<>();
         
         set.add(1);
         assertTrue(1 == set.size());
diff --git a/impl/src/test/java/jakarta/faces/model/ListenerTestImpl.java b/impl/src/test/java/jakarta/faces/model/ListenerTestImpl.java
index de1a9dcaeb..6e64bd48d2 100644
--- a/impl/src/test/java/jakarta/faces/model/ListenerTestImpl.java
+++ b/impl/src/test/java/jakarta/faces/model/ListenerTestImpl.java
@@ -27,7 +27,7 @@ public class ListenerTestImpl implements DataModelListener {
     public void rowSelected(DataModelEvent event) {
         Object rowData = event.getRowData();
         int rowIndex = event.getRowIndex();
-        trace("" + rowIndex);
+        trace(String.valueOf(rowIndex));
         if ((rowIndex >= 0) && (rowData == null)) {
             throw new IllegalArgumentException("rowIndex=" + rowIndex
                     + " but rowData is null");