Add performance metrics and refactor various classes

Added code to measure execution time in `UsePerson.java`.
Refactored `UsePerson.java`, `Person.java`, `Golfer.java`, `FileFilterTest.java`, and `LoopsSortsAndIfs.java` for clarity, usability, and performance.
Created `CompanyEmployee.java` and `LazyMessageSupplierTest.java` to implement interfaces and testing, respectively.
Made amendments in the test classes `CompanyEmployeeTest.java` and `FileFilterTest.java`.

src/main/java/interfaces/CompanyEmployee.java

@@ -0,0 +1,31 @@
+package interfaces;
+
+public class CompanyEmployee implements Company, Employee {
+
+    private final String first;
+    private final String last;
+
+    public CompanyEmployee(String first, String last) {
+        this.first = first;
+        this.last = last;
+    }
+
+    public String getName() {
+        return Employee.super.getName() + " works for " + Company.super.getName();
+    }
+
+    @Override
+    public String getFirst() {
+        return first;
+    }
+
+    @Override
+    public String getLast() {
+        return last;
+    }
+
+    @Override
+    public void doWork() {
+        System.out.println("Converting caffeine into code for $$$");
+    }
+}

src/main/java/lambdas/Person.java

@@ -30,9 +30,7 @@ public void setName(String name) {
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
-        if (!(o instanceof Person)) return false;
-
-        Person person = (Person) o;
+        if (!(o instanceof Person person)) return false;
 
         return Objects.equals(name, person.name);
     }

src/main/java/lambdas/UsePerson.java

@@ -22,11 +22,15 @@ public static void main(String[] args) {
                 .collect(Collectors.toList());  // Converts Stream<Person> to List<Person>
         System.out.println(people);
 
+        long startTime = System.nanoTime();
         people = names.stream()
+                .peek(name -> System.out.println(name + " on thread " + Thread.currentThread().getName()))
                 .map(Person::new) // uses the Person(String) ctr
                 // .map(Person::new) // uses the Person(Person) ctr
-                .collect(Collectors.toList());
+                .collect(Collectors.toList());  // reduction operation
+        long endTime = System.nanoTime();
         System.out.println(people);
+        System.out.println("Time taken: " + (endTime - startTime) / 1_000_000 + " ms");
 
         Person[] peopleArray = names.stream()
                 .map(Person::new)
@@ -37,7 +41,7 @@ public static void main(String[] args) {
         List<String> fullNames = Arrays.asList(
                 "John Lennon", "Paul McCartney", "George Harrison", "Ringo Starr");
         people = fullNames.stream()
-                .map(name -> name.split(" "))
+                .map(name -> name.split("\\s+"))
                 .map(Person::new) // use the Person(String...) ctr
                 .collect(Collectors.toList());
         System.out.println(people);

src/main/java/refactoring/after/LoopsSortsAndIfs.java

@@ -1,30 +1,16 @@
 package refactoring.after;
 
-import java.util.ArrayList;
-import java.util.Collections;
+import java.util.Arrays;
 import java.util.Comparator;
-import java.util.List;
 
 public class LoopsSortsAndIfs {
     public static void main(String[] args) {
-        String[] strings = "this is an array of strings".split(" ");
 
-        List<String> evenLengths = new ArrayList<>();
-        for (String s : strings) {
-            if (s.length() % 2 == 0) {
-                evenLengths.add(s.toUpperCase());
-            }
-        }
-
-        Collections.sort(evenLengths, new Comparator<String>() {
-            @Override
-            public int compare(String s1, String s2) {
-                return s1.length() - s2.length();
-            }
-        });
-
-        for (String s : evenLengths) {
-            System.out.println(s);
-        }
+        Arrays.stream("this is an array of strings".split(" "))
+                .filter(s -> s.length() % 2 == 0)
+                .map(String::toUpperCase)
+                .sorted(Comparator.comparingInt(String::length)
+                        .thenComparing(Comparator.naturalOrder()))
+                .forEach(System.out::println);
     }
 }

src/main/java/sorting/Golfer.java

@@ -1,5 +1,7 @@
 package sorting;
 
+import java.util.Objects;
+
 public class Golfer implements Comparable<Golfer> {
     private String first;
     private String last;
@@ -54,8 +56,8 @@ public boolean equals(Object o) {
 
         Golfer golfer = (Golfer) o;
 
-        if (first != null ? !first.equals(golfer.first) : golfer.first != null) return false;
-        return last != null ? last.equals(golfer.last) : golfer.last == null;
+        if (!Objects.equals(first, golfer.first)) return false;
+        return Objects.equals(last, golfer.last);
 
     }
 

src/test/java/interfaces/CompanyEmployeeTest.java

@@ -2,6 +2,8 @@
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 // Create a class called CompanyEmployee that implements both
 //   the Company and Employee interfaces
 // Implement the necessary methods
@@ -11,7 +13,7 @@ public class CompanyEmployeeTest {
 
     @Test
     public void getName() {
-//        CompanyEmployee emp = new CompanyEmployee("Peter", "Gibbons");
-//        assertEquals("Peter Gibbons works for Initech", emp.getName());
+        var emp = new CompanyEmployee("Peter", "Gibbons");
+        assertEquals("Peter Gibbons works for Initech", emp.getName());
     }
 }

src/test/java/lambdas/FileFilterTest.java

@@ -9,6 +9,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+@SuppressWarnings({"Convert2Lambda", "Anonymous2MethodRef"})
 public class FileFilterTest {
     private final File root = new File("src/main/java");
 
@@ -33,7 +34,7 @@ public boolean accept(File pathname) {
 
     @Test
     public void listDirectories_expressionLambda() {
-        File[] directories = root.listFiles(pathname -> pathname.isDirectory());
+        File[] directories = root.listFiles(File::isDirectory);
         assert directories != null;
         assertEquals(14, directories.length);
     }
@@ -50,7 +51,8 @@ public void listDirectories_blockLambda() {
 
     @Test
     public void listDirectories_assignToVariable() {
-        FileFilter filter = pathname -> pathname.isDirectory();
+        //FileFilter filter = pathname -> pathname.isDirectory();
+        FileFilter filter = File::isDirectory;
         File[] directories = root.listFiles(filter);
         assert directories != null;
         assertEquals(14, directories.length);
@@ -76,7 +78,8 @@ void iterate_over_map() {
         map.forEach((k, v) -> System.out.println(k + " -> " + v));
 
         var list = List.of("a", "b", "c");
-        list.forEach(x -> System.out.println(x));
+        list.forEach(x -> System.out.println("the value of x is " + x));
+        list.forEach(System.out::println);
     }
 
 }

src/test/java/lambdas/LazyMessageSupplierTest.java

@@ -0,0 +1,35 @@
+package lambdas;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.logging.Logger;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class LazyMessageSupplierTest {
+    private final Logger logger = Logger.getLogger(LazyMessageSupplierTest.class.getName());
+
+    private String getErrorMessage() {
+        System.out.println("Generating error message...");
+        return "An error occurred";
+    }
+
+    private String getLogMessage() {
+        System.out.println("Generating log message...");
+        return "A log message";
+    }
+
+    @Test
+    void testBoolean() {
+        boolean x = true;
+        logger.fine(getLogMessage());
+        assertTrue(x, getErrorMessage());
+    }
+
+    @Test
+    void testBooleanWithLazyErrorMessage() {
+        boolean x = true;
+        logger.fine(() -> getLogMessage());
+        assertTrue(x, () -> getErrorMessage());
+    }
+}