/*

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 /*

  * This file is available under and governed by the GNU General Public

  * License version 2 only, as published by the Free Software Foundation.

  * However, the following notice accompanied the original version of this

  * file:

  *

  * Written by Doug Lea with assistance from members of JCP JSR-166

  * Expert Group and released to the public domain, as explained at

  * http://creativecommons.org/publicdomain/zero/1.0/

  */

 package java.util.concurrent;

 /**

  * A recursive result-bearing {@link ForkJoinTask}.

  *

  * <p>For a classic example, here is a task computing Fibonacci numbers:

  *

  *  <pre> {@code

  * class Fibonacci extends RecursiveTask<Integer> {

  *   final int n;

  *   Fibonacci(int n) { this.n = n; }

  *   Integer compute() {

  *     if (n <= 1)

  *        return n;

  *     Fibonacci f1 = new Fibonacci(n - 1);

  *     f1.fork();

  *     Fibonacci f2 = new Fibonacci(n - 2);

  *     return f2.compute() + f1.join();

  *   }

  * }}</pre>

  *

  * However, besides being a dumb way to compute Fibonacci functions

  * (there is a simple fast linear algorithm that you'd use in

  * practice), this is likely to perform poorly because the smallest

  * subtasks are too small to be worthwhile splitting up. Instead, as

  * is the case for nearly all fork/join applications, you'd pick some

  * minimum granularity size (for example 10 here) for which you always

  * sequentially solve rather than subdividing.

  *

  * @since 1.7

  * @author Doug Lea

  */

 public abstract class RecursiveTask<V> extends ForkJoinTask<V> {

     private static final long serialVersionUID = 5232453952276485270L;

     /**

      * The result of the computation.

      */

     V result;

     /**

      * The main computation performed by this task.

      */

     protected abstract V compute();

     public final V getRawResult() {

         return result;

     }

     protected final void setRawResult(V value) {

         result = value;

     }

     /**

      * Implements execution conventions for RecursiveTask.

      */

     protected final boolean exec() {

         result = compute();

         return true;

     }

 }