    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 java.util.concurrent.Callable;
    020    import java.util.concurrent.Executor;
    021    import java.util.concurrent.FutureTask;
    022
    023    import 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     */
    036    public 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    }