modificato arraysequence in fake e aggiunti una nuova versione. fidato alcuni metodi che restituivano void invece di position. sono necessari ulteriori test

position/NodePositionList.java

@@ -79,21 +79,22 @@ public class NodePositionList<E> implements PositionList<E> {
     return next;
   }
 
-  public void addBefore(Position<E> p, E element)         throws InvalidPositionException {
+  public Position<E> addBefore(Position<E> p, E element)         throws InvalidPositionException {
     DNode<E> v = checkPosition(p);
     numElts++;
     DNode<E> newNode = new DNode<E>(v.getPrev(), v, element);
     v.getPrev().setNext(newNode);
     v.setPrev(newNode);
+    return newNode;
   }
 
-  public void addAfter(Position<E> p, E element) 
-      throws InvalidPositionException {
+  public Position<E> addAfter(Position<E> p, E element) throws InvalidPositionException {
     DNode<E> v = checkPosition(p);
     numElts++;
     DNode<E> newNode = new DNode<E>(v, v.getNext(), element);
     v.getNext().setPrev(newNode);
     v.setNext(newNode);
+    return newNode;
   }
 
   public void addFirst(E element) {

position/PositionList.java

@@ -27,9 +27,9 @@ public interface PositionList<E>  {
 
   public void addLast(E e);
 
-  public void addAfter(Position<E> p, E e)         throws InvalidPositionException;
+  public Position<E> addAfter(Position<E> p, E e)         throws InvalidPositionException;
 
-  public void addBefore(Position<E> p, E e)       throws InvalidPositionException;
+  public Position<E> addBefore(Position<E> p, E e)       throws InvalidPositionException;
 
   public E remove(Position<E> p) throws InvalidPositionException;