assertFalse(Files.exists(symlink, NOFOLLOW_LINKS));
      assertTrue(Files.isDirectory(realSymlinkTarget, NOFOLLOW_LINKS));
    }
  }

  /**
   * Starts a new task on the given executor that switches (deletes and replaces) a file between
   * being a directory and being a symlink. The given {@code file} is the file that should switch

   * implementation. Experimentally determined.
   */
  private static final int MAX_HASH_BUCKET_LENGTH = 9;

  // See CompactHashMap for a detailed description of how the following fields work. That
  // description talks about `keys`, `values`, and `entries`; here the `keys` and `values` arrays
  // are replaced by a single `elements` array but everything else works similarly.

  /**
   * The hashtable object. This can be either:
   *

       *   user task -- which means that we already got past this code (or else we exited early
       *   above))
       */
      // Unconditionally set; there is no risk of throwing away a queued task from another thread,
      // because in order for the current task to run on this executor the previous task must have
      // already started execution. Because each task on a TaskNonReentrantExecutor can only produce

            AbstractService service, ScheduledExecutorService executor, Runnable task) {
          return new FutureAsCancellable(
              executor.scheduleWithFixedDelay(task, initialDelay, delay, unit));
        }
      };
    }

    /**
     * Returns a {@link Scheduler} that schedules the task using the {@link
     * ScheduledExecutorService#scheduleAtFixedRate} method.
     *

  @CheckForNull private volatile InterruptibleTask<?> task;

  TrustedListenableFutureTask(Callable<V> callable) {
    this.task = new TrustedFutureInterruptibleTask(callable);
  }

  TrustedListenableFutureTask(AsyncCallable<V> callable) {
    this.task = new TrustedFutureInterruptibleAsyncTask(callable);
  }

  @Override
  public void run() {
    InterruptibleTask<?> localTask = task;
    if (localTask != null) {

public final class InterruptibleTaskTest extends TestCase {

  // Regression test for a deadlock where a task could be stuck busy waiting for the task to
  // transition to DONE
  public void testInterruptThrows() throws Exception {
    final CountDownLatch isInterruptibleRegistered = new CountDownLatch(1);
    InterruptibleTask<@Nullable Void> task =
        new InterruptibleTask<@Nullable Void>() {
          @Override

  public <T extends @Nullable Object> Future<T> submit(Callable<T> task) {
    return delegate().submit(task);
  }

  @Override
  public Future<?> submit(Runnable task) {
    return delegate().submit(task);
  }

  @Override
  public <T extends @Nullable Object> Future<T> submit(
      Runnable task, @ParametricNullness T result) {
    return delegate().submit(task, result);
  }

   * running with have the given name.
   *
   * @param task The Runnable to wrap
   * @param nameSupplier The supplier of thread names, {@link Supplier#get get} will be called once
   *     for each invocation of the wrapped callable.
   */
  @J2ktIncompatible
  @GwtIncompatible // threads
  static Runnable threadRenaming(Runnable task, Supplier<String> nameSupplier) {
    checkNotNull(nameSupplier);

   * MoreExecutors#newDirectExecutorService} and subject to the same constraints.
   *
   * <p>Although all tasks are immediately executed in the thread that submitted the task, this
   * {@code ExecutorService} imposes a small locking overhead on each task submission in order to
   * implement shutdown and termination behavior.
   *
   * <p>Because of the nature of single-thread execution, the methods {@code scheduleAtFixedRate}

            new AsyncCallable<String>() {
              @Override
              public ListenableFuture<String> call() throws Exception {
                // Make this executor terminate after this task so that the test can tell when
                // futureResult has received resultOfCombiner.
                executor.shutdown();
                callableBlocking.await();
                return resultOfCombiner;