/*
 * addAtIndex( ):
index < 0 : do nothing.
index > size: add to end
 *
 */
	public void addAtIndex(int index, E data) {
		if (index < 0)
			return;
		if (index > size())
			add(data);
		if (data != null)
			head = addAtIndex(head, index, data);
	}

	private LLNode<E> addAtIndex(LLNode<E> t, int index, E data) {
		LLNode<E> n;
		if (index == 0) {
			n = new LLNode<E>(data); // make new node
			n.setNext(t); // point to current node
			t = n; // check
		}

		else {
			t.setNext(addAtIndex(t.getNext(), index-1, data));
		}

		return t;

	}