/**
* Method removes a subscriber from a list of subscription. if there are no more subscribers to
* the specified message, method removes it from the list as well.
*
* @param messageId - a legal message identifier. Can't be < 0.
* @param subscriber - a subscriber that needs to be add to the list.
* @throws {@link IllegalArgumentException} if messageId < 0 or subscriber == null
* @return true on success, false otherwise.
*/
boolean unsubscribe(int messageId, Subscriber subscriber) {
if (messageId < 0 || subscriber == null) throw new IllegalArgumentException();
return _subscribers.remove(messageId, subscriber);
}
/**
* Notifies all subscribers about with specified message.
*
* @param message - message that is to notify subscribers.
*/
void dispatch(SystemMessage message) {
for (Subscriber s : _subscribers.get(message.ID)) {
s.onNotify(message);
}
}
/**
* Method adds a subscriber and a message that it's subscribed to to a list of subscribers.
*
* @param messageId - a legal message identifier. Can't be < 0.
* @param subscriber - a subscriber that needs to be add to the list.
* @throws {@link IllegalArgumentException} if messageId < 0 or subscriber == null
* @return true on success, false if the subscriber is already subscribed to the message.
*/
void subscribe(int messageId, Subscriber subscriber) {
if (messageId < 0 || subscriber == null) throw new IllegalArgumentException();
_subscribers.put(messageId, subscriber);
}