static final Object EVENT = new Object();

  abstract H createSubscriber();

  private @Nullable H subscriber;

  H getSubscriber() {
    return subscriber;
  }

  @Override
  protected void setUp() throws Exception {
    subscriber = createSubscriber();
    EventBus bus = new EventBus();
    bus.register(subscriber);
    bus.post(EVENT);
  }

  @Override

   * </ul>
   *
   * <p>This method is {@code protected} so that classes like {@code
   * com.google.common.util.concurrent.SettableFuture} do not expose it to their users as an
   * instance method. In the unlikely event that you need to call this method, call {@link
   * InternalFutures#tryInternalFastPathGetFailure(InternalFutureFailureAccess)}.
   */
  protected abstract
      Throwable tryInternalFastPathGetFailure();

 * specified the JVM flag {@code -XX:+DisableExplicitGC}. But in practice, it works very well for
 * ordinary tests.
 *
 * <p>Failure of the expected event to occur within an implementation-defined "reasonable" time
 * period or an interrupt while waiting for the expected event will result in a {@link
 * RuntimeException}.
 *
 * <p>Here's an example that tests a {@code finalize} method:
 *
 * <pre>{@code

   * behavior of futures so that you can contrast the next test with it.
   */
  public void testRegularFutureInterrupted() throws ExecutionException {

    /*
     * Here's the order of events that we want.
     *
     * 1. The client thread begins to block on a get() call to a future.
     * 2. The client thread is interrupted sometime before the result would be
     *   available.

        Platform.tryWeakKeys(new MapMaker()).makeMap();

    private Integer getUid(Object obj) {
      Integer uid = uids.get(obj);
      if (uid == null) {
        // One or more integer values could be skipped in the event of a race
        // to generate a UID for the same object from multiple threads, but
        // that shouldn't be a problem.
        uid = counter.getAndIncrement();
        Integer alreadySet = uids.putIfAbsent(obj, uid);

    // is called within doStart() so we know that the service cannot terminate or fail concurrently
    // with adding this listener so it is impossible to miss an event that we are interested in.
    addListener(
        new Listener() {
          @Override
          public void terminated(State from) {
            executor.shutdown();
          }

          @Override

   *
   * @param event event to post.
   */
  public void post(Object event) {
    Iterator<Subscriber> eventSubscribers = subscribers.getSubscribers(event);
    if (eventSubscribers.hasNext()) {
      dispatcher.dispatch(event, eventSubscribers);
    } else if (!(event instanceof DeadEvent)) {
      // the event had no subscribers and was not itself a DeadEvent
      post(new DeadEvent(this, event));
    }
  }

  @Override

    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 2));
    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 3));
    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 4));
    queue.enqueue(THROWING_EVENT);
    assertEquals(0, counters.size());
    queue.dispatch();

/**
 * Registry of subscribers to a single event bus.
 *
 * @author Colin Decker
 */
@ElementTypesAreNonnullByDefault
final class SubscriberRegistry {

  /**
   * All registered subscribers, indexed by event type.
   *
   * <p>The {@link CopyOnWriteArraySet} values make it easy and relatively lightweight to get an
   * immutable snapshot of all current subscribers to an event without any locking.
   */

            holder.set(str);
            deliveries.incrementAndGet();
          }
        });

    String EVENT = "Hello!";
    bus.post(EVENT);

    assertEquals("Only one event should be delivered.", 1, deliveries.get());
    assertEquals("Correct string should be delivered.", EVENT, holder.get());
  }