001/*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.util.concurrent;
018
019import com.google.common.annotations.GwtCompatible;
020
021import java.util.concurrent.ExecutionException;
022import java.util.concurrent.Future;
023
024import javax.annotation.Nullable;
025
026/**
027 * A callback for accepting the results of a {@link java.util.concurrent.Future}
028 * computation asynchronously.
029 *
030 * <p>To attach to a {@link ListenableFuture} use {@link Futures#addCallback}.
031 *
032 * @author Anthony Zana
033 * @since 10.0
034 */
035@GwtCompatible
036public interface FutureCallback<V> {
037  /**
038   * Invoked with the result of the {@code Future} computation when it is
039   * successful.
040   */
041  void onSuccess(@Nullable V result);
042
043  /**
044   * Invoked when a {@code Future} computation fails or is canceled.
045   *
046   * <p>If the future's {@link Future#get() get} method throws an {@link
047   * ExecutionException}, then the cause is passed to this method. Any other
048   * thrown object is passed unaltered.
049   */
050  void onFailure(Throwable t);
051}