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 com.google.common.annotations.Beta;
020
021import java.util.concurrent.Callable;
022import java.util.concurrent.Executor;
023import java.util.concurrent.FutureTask;
024
025/**
026 * A {@link FutureTask} that also implements the {@link ListenableFuture}
027 * interface.  Subclasses must make sure to call {@code super.done()} if they
028 * also override the {@link #done()} method, otherwise the listeners will not
029 * be called.
030 * 
031 * @author Sven Mawson
032 * @since 1
033 */
034@Beta
035public class ListenableFutureTask<V> extends FutureTask<V>
036    implements ListenableFuture<V> {
037
038  // The execution list to hold our listeners.
039  private final ExecutionList executionList = new ExecutionList();
040  
041  /**
042   * Creates a {@code ListenableFutureTask} that will upon running, execute the
043   * given {@code Callable}.
044   *
045   * @param  callable the callable task
046   * @throws NullPointerException if callable is null
047   */
048  public ListenableFutureTask(Callable<V> callable) {
049    super(callable);
050  }
051
052  /**
053   * Creates a {@code ListenableFutureTask} that will upon running, execute the
054   * given {@code Runnable}, and arrange that {@code get} will return the
055   * given result on successful completion.
056   *
057   * @param  runnable the runnable task
058   * @param result the result to return on successful completion. If
059   * you don't need a particular result, consider using
060   * constructions of the form:
061   * {@code ListenableFuture<?> f =
062   *     new ListenableFutureTask<Object>(runnable, null)}
063   * @throws NullPointerException if runnable is null
064   */
065  public ListenableFutureTask(Runnable runnable, V result) {
066    super(runnable, result);
067  }
068
069  @Override
070  public void addListener(Runnable listener, Executor exec) {
071    executionList.add(listener, exec);
072  }
073  
074  @Override
075  protected void done() {
076    executionList.run();
077  }
078}