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    
017    package com.google.common.util.concurrent;
018    
019    import com.google.common.annotations.Beta;
020    
021    import java.util.concurrent.Callable;
022    import java.util.concurrent.Executor;
023    import 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
035    public 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    }