* across calls to multiple listeners. Specifically, a given listener will have its callbacks
   * invoked in the same order as the underlying service enters those states. Additionally, at most
   * one of the listener's callbacks will execute at once. However, multiple listeners' callbacks
   * may execute concurrently, and listeners may execute in an order different from the one in which
   * they were registered.

    Listener listener;
    synchronized (this) {
      listener = listeners.get(state);
    }

    if (code == null || listener == null) {
      return new MockResponse()
          .setResponseCode(404)
          .setBody("unexpected request");
    }

    try {
      OAuthSession session = slackApi.exchangeCode(code, redirectUrl());
      listener.sessionGranted(session);

    super(callable);
  }

  ListenableFutureTask(Runnable runnable, @ParametricNullness V result) {
    super(runnable, result);
  }

  @Override
  public void addListener(Runnable listener, Executor exec) {
    executionList.add(listener, exec);
  }

  @CanIgnoreReturnValue
  @Override
  @ParametricNullness
  public V get(long timeout, TimeUnit unit)
      throws TimeoutException, InterruptedException, ExecutionException {

      return delegate;
    }

    @Override
    public void addListener(Runnable listener, Executor exec) {
      executionList.add(listener, exec);

      // When a listener is first added, we run a task that will wait for the delegate to finish,
      // and when it is done will run the listeners.
      if (hasListeners.compareAndSet(false, true)) {
        if (delegate.isDone()) {

   * MoreExecutors#directExecutor}. Otherwise, avoid it: See the warnings on the docs for {@code
   * directExecutor}.
   *
   * <p>This is the most general listener interface. For common operations performed using
   * listeners, see {@link Futures}. For a simplified but general listener interface, see {@link
   * Futures#addCallback addCallback()}.
   *

     * and then. This means that we're silently swallowing an exception -- maybe even an Error. But
     * this is no worse than what FutureTask does in that situation. Additionally, because the
     * Future was cancelled, its listeners have been run, so its consumers will not hang.
     *
     * Contrast this to the situation we have if setResult() throws, a situation described below.
     */
    I sourceResult;
    try {

    super(callable);
  }

  ListenableFutureTask(Runnable runnable, @ParametricNullness V result) {
    super(runnable, result);
  }

  @Override
  public void addListener(Runnable listener, Executor exec) {
    executionList.add(listener, exec);
  }

  @CanIgnoreReturnValue
  @Override
  @ParametricNullness
  public V get(long timeout, TimeUnit unit)
      throws TimeoutException, InterruptedException, ExecutionException {

    exec.shutdown();
    exec.awaitTermination(100, MILLISECONDS);
  }

  /**
   * Tests that all listeners complete, even if they were added before or after the future was
   * finishing. Also acts as a concurrency test to make sure the locking is done correctly when a
   * future is finishing so that no listeners can be lost.
   */
  public void testAllListenersCompleteSuccessfully()

    RecordingListener listener = new RecordingListener();
    manager.addListener(listener, directExecutor());
    manager.startAsync().awaitHealthy();
    assertTrue(manager.isHealthy());
    assertTrue(listener.healthyCalled);
    assertFalse(listener.stoppedCalled);
    assertTrue(listener.failedServices.isEmpty());
    manager.stopAsync().awaitStopped();

    exec.shutdown();
    exec.awaitTermination(100, MILLISECONDS);
  }

  /**
   * Tests that all listeners complete, even if they were added before or after the future was
   * finishing. Also acts as a concurrency test to make sure the locking is done correctly when a
   * future is finishing so that no listeners can be lost.
   */
  public void testAllListenersCompleteSuccessfully()