diff --git a/ratis-client/src/main/java/org/apache/ratis/client/api/AdminApi.java b/ratis-client/src/main/java/org/apache/ratis/client/api/AdminApi.java
index e27c8ae867..8ce6a5eb1b 100644
--- a/ratis-client/src/main/java/org/apache/ratis/client/api/AdminApi.java
+++ b/ratis-client/src/main/java/org/apache/ratis/client/api/AdminApi.java
@@ -68,7 +68,7 @@ default RaftClientReply setConfiguration(RaftPeer[] serversInNewConf, RaftPeer[]
   /** Transfer leadership to the given server.*/
   default RaftClientReply transferLeadership(RaftPeerId newLeader, long timeoutMs) throws IOException {
     return transferLeadership(newLeader, null, timeoutMs);
-  };
+  }
 
   RaftClientReply transferLeadership(RaftPeerId newLeader, RaftPeerId leaderId, long timeoutMs) throws IOException;
 }
\ No newline at end of file
diff --git a/ratis-client/src/main/java/org/apache/ratis/client/impl/OrderedStreamAsync.java b/ratis-client/src/main/java/org/apache/ratis/client/impl/OrderedStreamAsync.java
index 3847adf03b..989c00cbbc 100644
--- a/ratis-client/src/main/java/org/apache/ratis/client/impl/OrderedStreamAsync.java
+++ b/ratis-client/src/main/java/org/apache/ratis/client/impl/OrderedStreamAsync.java
@@ -112,6 +112,7 @@ CompletableFuture<DataStreamReply> sendRequest(DataStreamRequestHeader header, O
     try {
       requestSemaphore.acquire();
     } catch (InterruptedException e){
+      Thread.currentThread().interrupt();
       return JavaUtils.completeExceptionally(IOUtils.toInterruptedIOException(
           "Interrupted when sending " + JavaUtils.getClassSimpleName(data.getClass()) + ", header= " + header, e));
     }
diff --git a/ratis-client/src/main/java/org/apache/ratis/client/impl/RaftClientImpl.java b/ratis-client/src/main/java/org/apache/ratis/client/impl/RaftClientImpl.java
index 579c2f56bf..e85e0ded9d 100644
--- a/ratis-client/src/main/java/org/apache/ratis/client/impl/RaftClientImpl.java
+++ b/ratis-client/src/main/java/org/apache/ratis/client/impl/RaftClientImpl.java
@@ -350,7 +350,7 @@ RaftClientReply handleNotLeaderException(RaftClientRequest request, NotLeaderExc
   }
 
   private void refreshPeers(Collection<RaftPeer> newPeers) {
-    if (newPeers != null && newPeers.size() > 0) {
+    if (newPeers != null && !newPeers.isEmpty()) {
       peers.set(newPeers);
       // also refresh the rpc proxies for these peers
       clientRpc.addRaftPeers(newPeers);
diff --git a/ratis-common/src/main/java/org/apache/ratis/conf/ReconfigurationBase.java b/ratis-common/src/main/java/org/apache/ratis/conf/ReconfigurationBase.java
index ea6ba225e4..6d4930e676 100644
--- a/ratis-common/src/main/java/org/apache/ratis/conf/ReconfigurationBase.java
+++ b/ratis-common/src/main/java/org/apache/ratis/conf/ReconfigurationBase.java
@@ -114,7 +114,7 @@ synchronized Daemon stop() {
    * Construct a ReconfigurableBase with the {@link RaftProperties}
    * @param properties raft properties.
    */
-  public ReconfigurationBase(String name, RaftProperties properties) {
+  protected ReconfigurationBase(String name, RaftProperties properties) {
     this.name = name;
     this.properties = properties;
     this.context = new Context();
diff --git a/ratis-common/src/main/java/org/apache/ratis/datastream/impl/DataStreamPacketImpl.java b/ratis-common/src/main/java/org/apache/ratis/datastream/impl/DataStreamPacketImpl.java
index 6be0300645..41e3a5e12b 100644
--- a/ratis-common/src/main/java/org/apache/ratis/datastream/impl/DataStreamPacketImpl.java
+++ b/ratis-common/src/main/java/org/apache/ratis/datastream/impl/DataStreamPacketImpl.java
@@ -33,7 +33,7 @@ public abstract class DataStreamPacketImpl implements DataStreamPacket {
   private final long streamId;
   private final long streamOffset;
 
-  public DataStreamPacketImpl(ClientId clientId, Type type, long streamId, long streamOffset) {
+  protected DataStreamPacketImpl(ClientId clientId, Type type, long streamId, long streamOffset) {
     this.clientId = clientId;
     this.type = type;
     this.streamId = streamId;
diff --git a/ratis-common/src/main/java/org/apache/ratis/util/JvmPauseMonitor.java b/ratis-common/src/main/java/org/apache/ratis/util/JvmPauseMonitor.java
index 2e84c11227..86038e697c 100644
--- a/ratis-common/src/main/java/org/apache/ratis/util/JvmPauseMonitor.java
+++ b/ratis-common/src/main/java/org/apache/ratis/util/JvmPauseMonitor.java
@@ -159,6 +159,7 @@ private void detectPause() {
     try {
       extraSleep = sleepTime.sleep();
     } catch (InterruptedException ie) {
+      Thread.currentThread().interrupt();
       return;
     }
 
diff --git a/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerCallListener.java b/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerCallListener.java
index 104f9883a0..77ae4c8f35 100644
--- a/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerCallListener.java
+++ b/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerCallListener.java
@@ -30,7 +30,6 @@ public class MetricServerCallListener<R> extends ForwardingServerCallListener<R>
 
   MetricServerCallListener(
       ServerCall.Listener<R> delegate,
-      String metricNamePrefix,
       MessageMetrics metrics
   ){
     this.delegate = delegate;
diff --git a/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerInterceptor.java b/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerInterceptor.java
index a11d5ca160..7e20946add 100644
--- a/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerInterceptor.java
+++ b/ratis-grpc/src/main/java/org/apache/ratis/grpc/metrics/intercept/server/MetricServerInterceptor.java
@@ -76,7 +76,7 @@ public <R, S> ServerCall.Listener<R> interceptCall(
     String metricNamePrefix = getMethodMetricPrefix(method);
     ServerCall<R,S> monitoringCall = new MetricServerCall<>(call, metricNamePrefix, metrics);
     return new MetricServerCallListener<>(
-        next.startCall(monitoringCall, requestHeaders), metricNamePrefix, metrics);
+        next.startCall(monitoringCall, requestHeaders), metrics);
   }
 
   @Override
diff --git a/ratis-grpc/src/main/java/org/apache/ratis/grpc/server/GrpcServerProtocolClient.java b/ratis-grpc/src/main/java/org/apache/ratis/grpc/server/GrpcServerProtocolClient.java
index 2eb73f6aa0..e4a8549d39 100644
--- a/ratis-grpc/src/main/java/org/apache/ratis/grpc/server/GrpcServerProtocolClient.java
+++ b/ratis-grpc/src/main/java/org/apache/ratis/grpc/server/GrpcServerProtocolClient.java
@@ -102,7 +102,6 @@ private ManagedChannel buildChannel(RaftPeer target, int flowControlWindow,
   @Override
   public void close() {
     LOG.info("{} Close channels", raftPeerId);
-    CompletableFuture<Void> future1;
     if (useSeparateHBChannel) {
       GrpcUtil.shutdownManagedChannel(hbChannel);
     }
diff --git a/ratis-netty/src/main/java/org/apache/ratis/netty/server/NettyServerStreamRpc.java b/ratis-netty/src/main/java/org/apache/ratis/netty/server/NettyServerStreamRpc.java
index 2c53560535..b0acf2580e 100644
--- a/ratis-netty/src/main/java/org/apache/ratis/netty/server/NettyServerStreamRpc.java
+++ b/ratis-netty/src/main/java/org/apache/ratis/netty/server/NettyServerStreamRpc.java
@@ -310,6 +310,7 @@ public void close() {
       ConcurrentUtils.shutdownAndWait(TimeDuration.ONE_SECOND, workerGroup,
           timeout -> LOG.warn("{}: workerGroup shutdown timeout in " + timeout, this));
     } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
       LOG.error(this + ": Interrupted close()", e);
     }
 
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java
index dedc56cfc3..302f848719 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/LeaderElection.java
@@ -249,6 +249,9 @@ public void run() {
         }
       }
     } catch(Exception e) {
+      if (e instanceof InterruptedException) {
+          Thread.currentThread().interrupt();
+      }
       final LifeCycle.State state = lifeCycle.getCurrentState();
       if (state.isClosingOrClosed()) {
         LOG.info("{}: {} is safely ignored since this is already {}",
@@ -426,7 +429,7 @@ private ResultAndTerm waitForResults(Phase phase, long electionTerm, int submitt
         if (r.getServerReply().getSuccess()) {
           votedPeers.add(replierId);
           // If majority and all peers with higher priority have voted, candidate pass vote
-          if (higherPriorityPeers.size() == 0 && conf.hasMajority(votedPeers, server.getId())) {
+          if (higherPriorityPeers.isEmpty() && conf.hasMajority(votedPeers, server.getId())) {
             return logAndReturn(phase, Result.PASSED, responses, exceptions);
           }
         } else {
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
index 315d610551..07c0e6c4a2 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/ServerState.java
@@ -415,6 +415,9 @@ void close() {
         getStateMachineUpdater().stopAndJoin();
       }
     } catch (Throwable e) {
+      if (e instanceof InterruptedException) {
+          Thread.currentThread().interrupt();
+      }
       LOG.warn(getMemberId() + ": Failed to join " + getStateMachineUpdater(), e);
     }
     LOG.info("{}: applyIndex: {}", getMemberId(), getLastAppliedIndex());
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/impl/SnapshotManagementRequestHandler.java b/ratis-server/src/main/java/org/apache/ratis/server/impl/SnapshotManagementRequestHandler.java
index b899752e07..8632242b18 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/impl/SnapshotManagementRequestHandler.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/impl/SnapshotManagementRequestHandler.java
@@ -35,7 +35,7 @@
 import java.util.function.Supplier;
 
 class SnapshotManagementRequestHandler {
-  public static final Logger LOG = LoggerFactory.getLogger(TransferLeadership.class);
+  public static final Logger LOG = LoggerFactory.getLogger(SnapshotManagementRequestHandler.class);
 
   class PendingRequest {
     private final SnapshotManagementRequest request;
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/metrics/SegmentedRaftLogMetrics.java b/ratis-server/src/main/java/org/apache/ratis/server/metrics/SegmentedRaftLogMetrics.java
index e591473e8a..228258f300 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/metrics/SegmentedRaftLogMetrics.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/metrics/SegmentedRaftLogMetrics.java
@@ -187,6 +187,7 @@ public UncheckedAutoCloseable startPurgeTimer() {
     return Timekeeper.start(purgeTimer);
   }
 
+  @Override
   public void onStateMachineDataWriteTimeout() {
     numStateMachineDataWriteTimeout.inc();
   }
diff --git a/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/CacheInvalidationPolicy.java b/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/CacheInvalidationPolicy.java
index b8e57092fb..baae8e2ee6 100644
--- a/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/CacheInvalidationPolicy.java
+++ b/ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/CacheInvalidationPolicy.java
@@ -50,13 +50,13 @@ public List<LogSegment> evict(long[] followerNextIndices,
         long safeEvictIndex, long lastAppliedIndex,
         LogSegmentList segments, final int maxCachedSegments) {
       try(AutoCloseableLock readLock = segments.readLock()) {
-        return evictImpl(followerNextIndices, safeEvictIndex, lastAppliedIndex, segments, maxCachedSegments);
+        return evictImpl(followerNextIndices, safeEvictIndex, lastAppliedIndex, segments);
       }
     }
 
     private List<LogSegment> evictImpl(long[] followerNextIndices,
         long safeEvictIndex, long lastAppliedIndex,
-        LogSegmentList segments, final int maxCachedSegments) {
+        LogSegmentList segments) {
       List<LogSegment> result = new ArrayList<>();
       int safeIndex = segments.size() - 1;
       for (; safeIndex >= 0; safeIndex--) {
diff --git a/ratis-shell/src/main/java/org/apache/ratis/shell/cli/AbstractShell.java b/ratis-shell/src/main/java/org/apache/ratis/shell/cli/AbstractShell.java
index 139dd26e10..e2679045e5 100644
--- a/ratis-shell/src/main/java/org/apache/ratis/shell/cli/AbstractShell.java
+++ b/ratis-shell/src/main/java/org/apache/ratis/shell/cli/AbstractShell.java
@@ -43,7 +43,7 @@ public abstract class AbstractShell implements Closeable {
   /**
    * Creates a new instance of {@link AbstractShell}.
    */
-  public AbstractShell(Context context) {
+  protected AbstractShell(Context context) {
     closer = Closer.create();
     mCommands = loadCommands(context);
     // Register all loaded commands under closer.
diff --git a/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/command/AbstractParentCommand.java b/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/command/AbstractParentCommand.java
index ec8401f4f7..7293c5bf1e 100644
--- a/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/command/AbstractParentCommand.java
+++ b/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/command/AbstractParentCommand.java
@@ -29,7 +29,7 @@
 public abstract class AbstractParentCommand implements Command {
   private final Map<String, Command> subs;
 
-  public AbstractParentCommand(Context context, List<Function<Context, Command>> subCommandConstructors) {
+  protected AbstractParentCommand(Context context, List<Function<Context, Command>> subCommandConstructors) {
     this.subs = Collections.unmodifiableMap(subCommandConstructors.stream()
         .map(constructor -> constructor.apply(context))
         .collect(Collectors.toMap(Command::getCommandName, Function.identity(),
diff --git a/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/election/StepDownCommand.java b/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/election/StepDownCommand.java
index 50abfe37cd..02976ed347 100644
--- a/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/election/StepDownCommand.java
+++ b/ratis-shell/src/main/java/org/apache/ratis/shell/cli/sh/election/StepDownCommand.java
@@ -73,11 +73,6 @@ public String getDescription() {
     return description();
   }
 
-  @Override
-  public Options getOptions() {
-    return super.getOptions();
-  }
-
   /**
    * @return command's description
    */