001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent;
016
017import static java.lang.Math.min;
018import static java.util.concurrent.TimeUnit.NANOSECONDS;
019
020import com.google.common.annotations.GwtIncompatible;
021import com.google.common.annotations.J2ktIncompatible;
022import com.google.errorprone.annotations.CanIgnoreReturnValue;
023import java.util.concurrent.Callable;
024import java.util.concurrent.ExecutionException;
025import java.util.concurrent.Executor;
026import java.util.concurrent.FutureTask;
027import java.util.concurrent.TimeUnit;
028import java.util.concurrent.TimeoutException;
029import org.jspecify.annotations.Nullable;
030
031/**
032 * A {@link FutureTask} that also implements the {@link ListenableFuture} interface. Unlike {@code
033 * FutureTask}, {@code ListenableFutureTask} does not provide an overrideable {@link
034 * FutureTask#done() done()} method. For similar functionality, call {@link #addListener}.
035 *
036 * <p>Few users should use this class. It is intended primarily for those who are implementing an
037 * {@code ExecutorService}. Most users should call {@link ListeningExecutorService#submit(Callable)
038 * ListeningExecutorService.submit} on a service obtained from {@link
039 * MoreExecutors#listeningDecorator}.
040 *
041 * @author Sven Mawson
042 * @since 1.0
043 */
044@J2ktIncompatible
045@GwtIncompatible
046public class ListenableFutureTask<V extends @Nullable Object> extends FutureTask<V>
047    implements ListenableFuture<V> {
048  // TODO(cpovirk): explore ways of making ListenableFutureTask final. There are some valid reasons
049  // such as BoundedQueueExecutorService to allow extends but it would be nice to make it final to
050  // avoid unintended usage.
051
052  // The execution list to hold our listeners.
053  private final ExecutionList executionList = new ExecutionList();
054
055  /**
056   * Creates a {@code ListenableFutureTask} that will upon running, execute the given {@code
057   * Callable}.
058   *
059   * @param callable the callable task
060   * @since 10.0
061   */
062  public static <V extends @Nullable Object> ListenableFutureTask<V> create(Callable<V> callable) {
063    return new ListenableFutureTask<>(callable);
064  }
065
066  /**
067   * Creates a {@code ListenableFutureTask} that will upon running, execute the given {@code
068   * Runnable}, and arrange that {@code get} will return the given result on successful completion.
069   *
070   * @param runnable the runnable task
071   * @param result the result to return on successful completion. If you don't need a particular
072   *     result, consider using constructions of the form: {@code ListenableFuture<?> f =
073   *     ListenableFutureTask.create(runnable, null)}
074   * @since 10.0
075   */
076  public static <V extends @Nullable Object> ListenableFutureTask<V> create(
077      Runnable runnable, @ParametricNullness V result) {
078    return new ListenableFutureTask<>(runnable, result);
079  }
080
081  ListenableFutureTask(Callable<V> callable) {
082    super(callable);
083  }
084
085  ListenableFutureTask(Runnable runnable, @ParametricNullness V result) {
086    super(runnable, result);
087  }
088
089  @Override
090  public void addListener(Runnable listener, Executor exec) {
091    executionList.add(listener, exec);
092  }
093
094  @CanIgnoreReturnValue
095  @Override
096  @ParametricNullness
097  public V get(long timeout, TimeUnit unit)
098      throws TimeoutException, InterruptedException, ExecutionException {
099
100    long timeoutNanos = unit.toNanos(timeout);
101    if (timeoutNanos <= OverflowAvoidingLockSupport.MAX_NANOSECONDS_THRESHOLD) {
102      return super.get(timeout, unit);
103    }
104    // Waiting 68 years should be enough for any program.
105    return super.get(
106        min(timeoutNanos, OverflowAvoidingLockSupport.MAX_NANOSECONDS_THRESHOLD), NANOSECONDS);
107  }
108
109  /** Internal implementation detail used to invoke the listeners. */
110  @Override
111  protected void done() {
112    executionList.execute();
113  }
114}