CountingRunnable listener = new CountingRunnable();

    future.addListener(listener, directExecutor());
    listener.assertNotRun();

    future.set(1);
    listener.assertRun();
  }

  public void testListenLaterFailed() {
    CountingRunnable listener = new CountingRunnable();

    future.addListener(listener, directExecutor());
    listener.assertNotRun();

  }

  @Override
  @SuppressWarnings("CatchingUnchecked") // sneaky checked exception
  public void addListener(Runnable listener, Executor executor) {
    checkNotNull(listener, "Runnable was null.");
    checkNotNull(executor, "Executor was null.");
    try {
      executor.execute(listener);
    } catch (Exception e) { // sneaky checked exception

    checkNotNull(unit);
    return get();
  }

  @Override
  public void addListener(Runnable runnable, Executor executor) {
    Listener listener = new Listener(runnable, executor);
    if (isDone()) {
      listener.execute();
    } else {
      listeners.add(listener);
    }
  }

  @CanIgnoreReturnValue
  protected boolean setException(Throwable throwable) {
    checkNotNull(throwable);

    compound.addListener(listener, directExecutor());
    assertThat(getDone(compound)).isEmpty();
    assertTrue(listener.wasCalled());
  }

  public void testAllAsList_emptyArray() throws Exception {
    SingleCallListener listener = new SingleCallListener();
    listener.expectCall();
    ListenableFuture<List<String>> compound = allAsList();
    compound.addListener(listener, directExecutor());

       * lets all futures share the same listener.
       *
       * We store `localFutures` inside the listener because `this.futures` might be nulled out by
       * the time the listener runs for the final future -- at which point we need to check all
       * inputs for exceptions *if* we're collecting values. If we're not, then the listener doesn't
       * need access to the futures again, so we can just pass `null`.

   *   <li>When a {@code ListenableFuture} listener is registered to run under {@code
   *       directExecutor}, the listener can execute in any of three possible threads:
   *       <ol>
   *         <li>When a thread attaches a listener to a {@code ListenableFuture} that's already
   *             complete, the listener runs immediately in that thread.
   *         <li>When a thread attaches a listener to a {@code ListenableFuture} that's

    CountingRunnable listener = new CountingRunnable();

    future.addListener(listener, directExecutor());
    listener.assertNotRun();

    future.set(1);
    listener.assertRun();
  }

  public void testListenLaterFailed() {
    CountingRunnable listener = new CountingRunnable();

    future.addListener(listener, directExecutor());
    listener.assertNotRun();

    assertNull(segment.refresh(key, hash, identityLoader(), false));
  }

  // Removal listener tests

  public void testRemovalListener_explicit() {
    QueuingRemovalListener<Object, Object> listener = queuingRemovalListener();
    LocalCache<Object, Object> map = makeLocalCache(createCacheBuilder().removalListener(listener));
    assertTrue(listener.isEmpty());

    Object one = new Object();
    Object two = new Object();

    assertNull(segment.refresh(key, hash, identityLoader(), false));
  }

  // Removal listener tests

  public void testRemovalListener_explicit() {
    QueuingRemovalListener<Object, Object> listener = queuingRemovalListener();
    LocalCache<Object, Object> map = makeLocalCache(createCacheBuilder().removalListener(listener));
    assertTrue(listener.isEmpty());

    Object one = new Object();
    Object two = new Object();

      return UNSAFE.compareAndSwapObject(future, LISTENERS_OFFSET, expect, update);
    }

    /** Performs a GAS operation on the {@link #listeners} field. */
    @Override
    Listener gasListeners(AbstractFuture<?> future, Listener update) {
      while (true) {
        Listener listener = future.listeners;
        if (update == listener) {