private class AVLIterator<E> implements Iterator<E>{

		 private String[] stack;
		 public Node curr;
		 private int index = 0;

		 private AVLIterator(StackBlock s){
		         stack = s;
				 curr = stack[index];
			 }

		 public boolean hasNext(){

				 if(curr.next !=null){
					 return true;
				 }

				 else{
					 return false;
		        }
			 }

		 public Object next(){
		         if(hasNext() = false){
				     throw new NoSuchElementException();
					 }
			     else{
				     return stack[index++];
					 }

			 }

		  public void remove(){
		         throw new NoSuchElementException();
		 }

         }