* asynchronously.
 *
 * <p>To attach to a {@link ListenableFuture} use {@link Futures#addCallback}.
 *
 * @author Anthony Zana
 * @since 10.0
 */
@GwtCompatible
public interface FutureCallback<V extends @Nullable Object> {
  /** Invoked with the result of the {@code Future} computation when it is successful. */
  void onSuccess(@ParametricNullness V result);

  /**

    addCallback(f, callback, directExecutor());
    f.setException(e);
  }

  public void testCancel() {
    SettableFuture<String> f = SettableFuture.create();
    FutureCallback<String> callback =
        new FutureCallback<String>() {
          private final Object monitor = new Object();
          private boolean called = false;

          @Override
          public void onSuccess(String result) {

    addCallback(f, callback, directExecutor());
    f.setException(e);
  }

  public void testCancel() {
    SettableFuture<String> f = SettableFuture.create();
    FutureCallback<String> callback =
        new FutureCallback<String>() {
          private final Object monitor = new Object();
          private boolean called = false;

          @Override
          public void onSuccess(String result) {

    return new Promise<V>(
            (resolve, reject) -> {
              Futures.addCallback(
                  this,
                  new FutureCallback<V>() {
                    @Override
                    public void onSuccess(V value) {
                      resolve.onInvoke(value);
                    }

                    @Override

  }

  public void testAddCallback() {
    FluentFuture<String> f = FluentFuture.from(immediateFuture("a"));
    boolean[] called = new boolean[1];
    f.addCallback(
        new FutureCallback<String>() {
          @Override
          public void onSuccess(String result) {
            called[0] = true;
          }

          @Override
          public void onFailure(Throwable t) {}
        },

   * callbacks, but any callback added through this method is guaranteed to be called once the
   * computation is complete.
   *
   * <p>Example:
   *
   * {@snippet :
   * future.addCallback(
   *     new FutureCallback<QueryResult>() {
   *       public void onSuccess(QueryResult result) {
   *         storeInCache(result);
   *       }
   *       public void onFailure(Throwable t) {
   *         reportError(t);
   *       }

  public static <V extends @Nullable Object> void addCallback(
      ListenableFuture<V> future, FutureCallback<? super V> callback, Executor executor) {
    Preconditions.checkNotNull(callback);
    future.addListener(new CallbackListener<V>(future, callback), executor);
  }

  /** See {@link #addCallback(ListenableFuture, FutureCallback, Executor)} for behavioral notes. */

    checkNotNull(closingExecutor);
    ClosingFuture<C> closingFuture = new ClosingFuture<>(nonCancellationPropagating(future));
    Futures.addCallback(
        future,
        new FutureCallback<@Nullable AutoCloseable>() {
          @Override
          public void onSuccess(@Nullable AutoCloseable result) {
            closingFuture.state.closeables.closer.eventuallyClose(result, closingExecutor);
          }