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Scala example source code file (

This example Scala source code file ( is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

concurrent, forkjoin, forkjointask, recursivetask, v

The Scala example source code

 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at

package scala.concurrent.forkjoin;

 * 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;


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