Add a code snippet for anonymous classes (BAEL-2833) (#6690)

* Add a code snippet about anonymous classes (BAEL-2833)

Add a code snippet about anonymous classes (BAEL-2833)
Create module core-java-2 and move 'anonymous' package there

* Adjust the pom of core-java-8-2 module

* Adjust unit test

core-java-8-2/src/main/java/com/baeldung/anonymous/Book.java

@@ -0,0 +1,15 @@
+package com.baeldung.anonymous;
+
+public class Book {
+
+    final String title;
+    
+    public Book(String title) {
+        this.title = title;
+    }
+    
+    public String description() {
+        return "Title: " + title;
+    }
+
+}

core-java-8-2/src/main/java/com/baeldung/anonymous/Main.java

@@ -0,0 +1,64 @@
+package com.baeldung.anonymous;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Code snippet that illustrates the usage of anonymous classes.
+ * 
+ * Note that use of Runnable instances in this example does not demonstrate their
+ * common use.
+ * 
+ * @author A. Shcherbakov
+ *
+ */
+public class Main {
+
+    public static void main(String[] args) {
+        final List<Runnable> actions = new ArrayList<Runnable>(2);
+
+        Runnable action = new Runnable() {
+            @Override
+            public void run() {
+                System.out.println("Hello from runnable.");
+            }
+
+        };
+        actions.add(action);
+
+        Book book = new Book("Design Patterns") {
+            @Override
+            public String description() {
+                return "Famous GoF book.";
+            }
+        };
+
+        System.out.println(String.format("Title: %s, description: %s", book.title, book.description()));
+
+        actions.add(new Runnable() {
+            @Override
+            public void run() {
+                System.out.println("Hello from runnable #2.");
+
+            }
+        });
+
+        int count = 1;
+
+        Runnable action2 = new Runnable() {
+            static final int x = 0;
+            // static int y = 0;
+
+            @Override
+            public void run() {
+                System.out.println(String.format("Runnable with captured variables: count = %s, x = %s", count, x));
+            }
+        };
+        actions.add(action2);
+
+        for (Runnable a : actions) {
+            a.run();
+        }
+    }
+
+}

core-java-8-2/src/test/java/com/baeldung/UnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/**
+ * Unit test for simple App.
+ */
+public class UnitTest {
+    /**
+     * Stub test
+     */
+    @Test
+    public void givenPreconditions_whenCondition_shouldResult() {
+        assertTrue(true);
+    }
+}