SettableFuture<@Nullable Void> future = SettableFuture.create();
    Object unused =
        new Object() {
          @SuppressWarnings({"removal", "Finalize"}) // b/487687332
          @Override
          protected void finalize() {
            future.set(null);
          }
        };
    unused = null; // Hint to the JIT that unused is unreachable
    GcFinalization.awaitDone(future);
    assertTrue(future.isDone());

    }

    @Override
    public <T> Future<T> submit(Callable<T> task) {
      throw new UnsupportedOperationException();
    }

    @Override
    public Future<?> submit(Runnable task) {
      throw new UnsupportedOperationException();
    }

    @Override
    public <T> Future<T> submit(Runnable task, T result) {
      throw new UnsupportedOperationException();
    }

    SettableFuture<Integer> future = SettableFuture.create();
    assertTrue(future.set(42));
    // Later attempts to set the future should return false.
    assertFalse(future.set(23));
    assertFalse(future.setException(new Exception("bar")));
    assertFalse(future.setFuture(SettableFuture.create()));
    // Check that the future has been set properly.
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());

        return new ExecutionListWrapper() {
          final AbstractFuture<?> future = new AbstractFuture<Object>() {};

          @Override
          public void add(Runnable runnable, Executor executor) {
            future.addListener(runnable, executor);
          }

          @Override
          public void execute() {
            future.set(null);
          }

    assertFalse(future.isCancelled());

    ExecutorService executor = newSingleThreadExecutor();

    try {
      Future<Boolean> getResult = executor.submit(() -> future.get());

      // Release the future value.
      latch.countDown();

      assertTrue(getResult.get(10, SECONDS));
    } finally {
      executor.shutdownNow();
    }

    assertTrue(future.isDone());

    assertTrue(future.isDone());
    assertFalse(future.isCancelled());

    assertTrue(latch.await(5, SECONDS));
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());

    assertEquals(expectedValue, future.get());
  }

  public void testCancelledFuture() throws InterruptedException, ExecutionException {
    assertTrue(future.isDone());
    assertTrue(future.isCancelled());

      Future<?> possiblyIgnoredError = threadPool.submit(new Producer(q, 20));
      @SuppressWarnings("unused") // https://errorprone.info/bugpattern/FutureReturnValueIgnored
      Future<?> possiblyIgnoredError1 = threadPool.submit(new Producer(q, 20));
      @SuppressWarnings("unused") // https://errorprone.info/bugpattern/FutureReturnValueIgnored

    SettableFuture<Integer> future = SettableFuture.create();
    assertTrue(future.set(42));
    // Later attempts to set the future should return false.
    assertFalse(future.set(23));
    assertFalse(future.setException(new Exception("bar")));
    assertFalse(future.setFuture(SettableFuture.create()));
    // Check that the future has been set properly.
    assertTrue(future.isDone());
    assertFalse(future.isCancelled());

  /**
   * Retrieves the result of a {@code Future} known to be done but uses the {@code get(long,
   * TimeUnit)} overload in order to test that method.
   */
  static <V extends @Nullable Object> V getDoneFromTimeoutOverload(Future<V> future)
      throws ExecutionException {
    checkState(future.isDone(), "Future was expected to be done: %s", future);
    try {
      return getUninterruptibly(future, 0, SECONDS);
    } catch (TimeoutException e) {

@GwtIncompatible
public class MockFutureListener implements Runnable {
  private final CountDownLatch countDownLatch;
  private final ListenableFuture<?> future;

  public MockFutureListener(ListenableFuture<?> future) {
    this.countDownLatch = new CountDownLatch(1);
    this.future = future;

    future.addListener(this, directExecutor());
  }

  @Override
  public void run() {
    countDownLatch.countDown();
  }

  /**