add source code comments

Author: TiagoTi

examples/java/HelloWorldApp.java

@@ -1,3 +1,8 @@
+/**
+ * The HelloWorldApp class implements an application that
+ * simply prints "Hello World!" to standard output.
+ */
+
 class HelloWorldAppp {
 	public static void main(String[] args){
 		System.out.println("Hello World!");