public void registerCallbackWhenCacheEmpty(EventSubscriber aController, int notification) {
if (!callbackListeners.isEmpty()) {
Iterator<EventSubscriber> it = callbackListeners.iterator();
while (it.hasNext()) {
EventSubscriber es = (EventSubscriber) it.next();
if (es == aController) {
return;
}
}
} else if (notification == NotifyWhenRegistering) {