001/*
002 * Copyright (C) 2008 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 java.util.concurrent.Callable;
020import java.util.concurrent.Executor;
021import java.util.concurrent.FutureTask;
022
023import javax.annotation.Nullable;
024
025/**
026 * A {@link FutureTask} that also implements the {@link ListenableFuture}
027 * interface.  Unlike {@code FutureTask}, {@code ListenableFutureTask} does not
028 * provide an overrideable {@link FutureTask#done() done()} method.  For similar
029 * functionality, call {@link #addListener}.
030 * 
031 * <p>
032 *
033 * @author Sven Mawson
034 * @since 1.0
035 */
036public final class ListenableFutureTask<V> extends FutureTask<V>
037    implements ListenableFuture<V> {
038
039  // The execution list to hold our listeners.
040  private final ExecutionList executionList = new ExecutionList();
041
042  /**
043   * Creates a {@code ListenableFutureTask} that will upon running, execute the
044   * given {@code Callable}.
045   *
046   * @param callable the callable task
047   * @since 10.0
048   */
049  public static <V> ListenableFutureTask<V> create(Callable<V> callable) {
050    return new ListenableFutureTask<V>(callable);
051  }
052
053  /**
054   * Creates a {@code ListenableFutureTask} that will upon running, execute the
055   * given {@code Runnable}, and arrange that {@code get} will return the
056   * given result on successful completion.
057   *
058   * @param runnable the runnable task
059   * @param result the result to return on successful completion. If you don't
060   *     need a particular result, consider using constructions of the form:
061   *     {@code ListenableFuture<?> f = ListenableFutureTask.create(runnable,
062   *     null)}
063   * @since 10.0
064   */
065  public static <V> ListenableFutureTask<V> create(
066      Runnable runnable, @Nullable V result) {
067    return new ListenableFutureTask<V>(runnable, result);
068  }
069
070  private ListenableFutureTask(Callable<V> callable) {
071    super(callable);
072  }
073
074  private ListenableFutureTask(Runnable runnable, @Nullable V result) {
075    super(runnable, result);
076  }
077
078  @Override
079  public void addListener(Runnable listener, Executor exec) {
080    executionList.add(listener, exec);
081  }
082
083  /**
084   * Internal implementation detail used to invoke the listeners.
085   */
086  @Override
087  protected void done() {
088    executionList.execute();
089  }
090}