/**
 * Helper interface to implement both {@link ListenableFuture} and {@link ScheduledFuture}.
 *
 * @author Anthony Zana
 * @since 15.0
 */
@GwtCompatible
public interface ListenableScheduledFuture<V extends @Nullable Object>

  }

  private static class ImmediateScheduledFuture<V> extends SimpleForwardingListenableFuture<V>
      implements ListenableScheduledFuture<V> {
    static <V> ListenableScheduledFuture<V> of(V value) {
      return new ImmediateScheduledFuture<>(immediateFuture(value));
    }

    static <V> ListenableScheduledFuture<V> failed(Throwable t) {
      return new ImmediateScheduledFuture<>(immediateFailedFuture(t));
    }

    }

    @Override
    public void execute(Runnable runnable) {}

    @Override
    public <V> ListenableScheduledFuture<V> schedule(
        Callable<V> callable, long delay, TimeUnit unit) {
      return NeverScheduledFuture.create();
    }

    @Override
    public ListenableScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
      return NeverScheduledFuture.create();
    }

  /**
   * @since 15.0 (previously returned ScheduledFuture)
   */
  @Override
  ListenableScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit);

  /**
   * @since 15.0 (previously returned ScheduledFuture)
   */
  @Override
  <V extends @Nullable Object> ListenableScheduledFuture<V> schedule(
      Callable<V> callable, long delay, TimeUnit unit);

  /**

  }

  @Override
  public ListenableScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
    Preconditions.checkNotNull(command, "command must not be null");
    Preconditions.checkNotNull(unit, "unit must not be null!");
    return schedule(callable(command), delay, unit);
  }

  @Override
  public <V> ListenableScheduledFuture<V> schedule(

  }

  @Override
  public ListenableScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
    Preconditions.checkNotNull(command, "command must not be null");
    Preconditions.checkNotNull(unit, "unit must not be null!");
    return schedule(callable(command), delay, unit);
  }

  @Override
  public <V> ListenableScheduledFuture<V> schedule(

    }

    @Override
    public void execute(Runnable runnable) {}

    @Override
    public <V> ListenableScheduledFuture<V> schedule(
        Callable<V> callable, long delay, TimeUnit unit) {
      return NeverScheduledFuture.create();
    }

    @Override
    public ListenableScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
      return NeverScheduledFuture.create();
    }