public void addInOrderPointers(Node z){
		if (z != null){
			Node prev = treePredecessor(z);
			Node next = treeSuccessor(z);
			if (prev != null)
				prev.nextInOrder = z;
			if (next != null)
				next.prevInOrder = z;
			z.nextInOrder = next;
			z.prevInOrder = prev;
		}

	}
	public void delInOrderPointers(Node z){
		if (z != null){
			Node prev = z.prevInOrder;
			Node next = z.nextInOrder;
			if (prev != null)
				prev.nextInOrder = next;
			if (next != null)
				next.prevInOrder = prev;
		}