code: public void subscribeToEvent(final EventListener eventListener, final Class<? extends AbstractTaskEvent> eventType) {
  
  		synchronized (this.subscriptions) {
  
  			List<EventListener> subscribers = this.subscriptions.get(eventType);
  			if (subscribers == null) {
  				subscribers = new ArrayList<EventListener>();
  				this.subscriptions.put(eventType, subscribers);
  			}
  			subscribers.add(eventListener);
  		}
  
  	}
docs: Subscribes the given event listener object to the specified event type.
  
  @param eventListener
  the {@link EventListener} object to create the subscription for
  @param eventType
  the event type the given listener object wants to be notified about