Add constructors and tests for Person and file filtering

Implemented varargs and copy constructors for the Person class. Added various tests for filtering directories and Java source files, including methods with lambdas, method references, and anonymous inner classes.

src/main/java/lambdas/Person.java

@@ -2,6 +2,8 @@
 
 import java.util.Objects;
 
+// public record Person(String name) {}
+
 public class Person {
     private String name;
 
@@ -11,10 +13,12 @@ public Person(String name) {
         this.name = name;
     }
 
+    // copy constructor
     public Person(Person other) {
         this.name = other.name;
     }
 
+    // varargs constructor
     public Person(String... names) {
         this.name = String.join(" ", names);
     }

src/main/java/lambdas/UsePerson.java

@@ -24,7 +24,7 @@ public static void main(String[] args) {
 
         people = names.stream()
                 .map(Person::new) // uses the Person(String) ctr
-                // .map(Person::new) // uses the Person(Person) ctr
+                .map(Person::new) // uses the Person(Person) ctr
                 .collect(Collectors.toList());
         System.out.println(people);
 

src/test/java/lambdas/FileFilterTest.java

@@ -20,6 +20,7 @@ void listFiles() {
         assertEquals(22, files.length);
     }
 
+    @SuppressWarnings({"Convert2Lambda", "Anonymous2MethodRef"})
     @Test
     void listDirectories_anonInnerClass() {
         File[] directories = root.listFiles(new FileFilter() {
@@ -28,12 +29,22 @@ public boolean accept(File file) {
                 return file.isDirectory();
             }
         });
+        assert directories != null;
         assertEquals(14, directories.length);
     }
 
+    @SuppressWarnings("Convert2MethodRef")
     @Test
     void listDirectories_expressionLambda() {
         File[] directories = root.listFiles(file -> file.isDirectory());
+        assert directories != null;
+        assertEquals(14, directories.length);
+    }
+
+    @Test
+    void listDirectories_methodReference() {
+        File[] directories = root.listFiles(File::isDirectory);
+        assert directories != null;
         assertEquals(14, directories.length);
     }
 
@@ -43,13 +54,29 @@ void listDirectories_blockLambda() {
             System.out.println("Checking: " + file);
             return file.isDirectory();
         });
+        assert directories != null;
         assertEquals(14, directories.length);
     }
 
     @Test
     void listDirectories_assignedToVariable() {
-        FileFilter filter = (File file) -> file.isDirectory();
+        FileFilter filter = File::isDirectory;
         File[] directories = root.listFiles(filter);
+        assert directories != null;
         assertEquals(14, directories.length);
     }
+
+    @Test
+    void listJavaSrcFiles_fileFilter() {
+        File[] javaFiles = root.listFiles(file -> file.getName().endsWith(".java"));
+        assert javaFiles != null;
+        assertEquals(8, javaFiles.length);
+    }
+
+    @Test
+    void listJavaSrcFiles_filenameFilter() {
+        File[] javaFiles = root.listFiles((dir, name) -> name.endsWith(".java"));
+        assert javaFiles != null;
+        assertEquals(8, javaFiles.length);
+    }
 }