public void Update() 
	{
		if (update) 
		{
			if (push) 
			{
				add(screens.peek());
				top = screens.peek();
				setVisible(true);
			} 
			else 
			{
				remove(screens.pop());
				top = screens.peek();
				top.repaint();
			}
			top.requestFocus();
			if(numpop == 0)
				update = false;
			else
				numpop--;
		}
	}