Created a Lambdas example for the callback pattern, using the same output of the traditional version. Have also added another unit test for issue #334

callback/src/main/java/com/iluwatar/callback/LambdasApp.java

@@ -0,0 +1,19 @@
+package com.iluwatar.callback;
+
+/**
+ *
+ * This example generates the exact same output as {@link App} however the callback has been
+ * defined as a Lambdas expression.
+ *
+ */
+public class LambdasApp {
+
+  /**
+   * Program entry point
+   */
+  public static void main(String[] args){
+    Task task = new SimpleTask();
+    Callback c = () -> System.out.println("I'm done now.");
+    task.executeWith(c);
+  }
+}