Class ScheduledUpdatesQueue

input/ScheduledUpdatesQueue.java:15–105

Event queue where simulation objects can request an update to happen at the specified simulation time. Multiple updates at the same time are merged to a single update.

 * are merged to a single update.
 */
public class ScheduledUpdatesQueue implements EventQueue {
	/** Time of the event (simulated seconds) */
	private ExternalEvent nextEvent;
	private List<ExternalEvent> updates;
	
	/**
	 * Constructor. Creates an empty update queue.
	 */
	public ScheduledUpdatesQueue(){
		this.nextEvent = new ExternalEvent(Double.MAX_VALUE);
		this.updates = new ArrayList<ExternalEvent>();
	}
	
	/**
	 * Returns the next scheduled event or event with time Double.MAX_VALUE
	 * if there aren't any. 
	 * @return the next scheduled event
	 */
	public ExternalEvent nextEvent() {
		ExternalEvent event = this.nextEvent;
		
		if (this.updates.size() == 0) {
			this.nextEvent = new ExternalEvent(Double.MAX_VALUE);
		}
		else {
			this.nextEvent = this.updates.remove(0);
		}
		
		return event;
	}
	
	/**
	 * Returns the next scheduled event's time or Double.MAX_VALUE if there
	 * aren't any events left
	 * @return the next scheduled event's time
	 */
	public double nextEventsTime() {
		return this.nextEvent.getTime();
	}

	/**
	 * Add a new update request for the given time
	 * @param simTime The time when the update should happen
	 */
	public void addUpdate(double simTime) {
		ExternalEvent ee = new ExternalEvent(simTime);

		if (ee.compareTo(nextEvent) == 0) { // this event is already next
			return;
		}
		else if (this.nextEvent.getTime() > simTime) { // new nextEvent
			putToQueue(this.nextEvent); // put the old nextEvent back to q
			this.nextEvent = ee;
		}
		else { // given event happens later..
			putToQueue(ee);
		}
	}