int index = (tabs_in_order.indexOf(tab) + 1)%tabs_in_order.size();
int index = tabs_in_order.indexOf(tab) - 1; if (index < 0) index = tabs_in_order.size() - 1;
		public void handleEvent(Event event) {			int index = (tabs_in_order.indexOf(tab) + 1)%tabs_in_order.size();			setTab((GraphicsTab)tabs_in_order.get(index));		}