implementato nodeposition con to string e reverse. aggiunto copyright

stack/ArrayStack.java

@@ -9,7 +9,8 @@ import exceptions.EmptyStackException;
  * Date: 05/03/14
  * Time: 0.12
  */
-
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 
 public class ArrayStack<E> implements Stack<E> {
 

stack/NodeStack.java

@@ -9,7 +9,8 @@ import stack.utility.Node;
  * Date: 05/03/14
  * Time: 0.12
  */
-
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 
 public class NodeStack<E> implements Stack<E> {