Java通過Fork/Join來優化平行計算

Java程式碼：

package Threads;

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;

/**
 * Created by Frank
 */
public class RecursiveActionDemo extends RecursiveAction {

    static int[] raw = {19, 3, 0, -1, 57, 24, 65, Integer.MAX_VALUE, 42, 0, 3, 5};
    static int[] sorted = null;
    int[] source;
    int[] dest;
    int length;
    int start;
    final static int THRESHOLD = 4;

    public static void main(String[] args) {
        sorted = new int[raw.length];

        ForkJoinPool pool = new ForkJoinPool();
        pool.invoke(new RecursiveActionDemo(raw, 0, raw.length, sorted));

        System.out.println('[');
        for (int i : sorted) {
            System.out.println(i + ",");
        }
        System.out.println(']');
    }

    public RecursiveActionDemo(int[] source, int start, int length, int[] dest) {
        this.source = source;
        this.dest = dest;
        this.length = length;
        this.start = start;
    }

    @Override
    protected void compute() {
        System.out.println("ForkJoinDemo.compute()");
        if (length < THRESHOLD) {    // 直接計算
            for (int i = start; i < start + length; i++) {
                dest[i] = source[i] * source[i];
            }
        } else { // 分而治之
            int split = length / 2;
            /**
             * invokeAll反覆呼叫fork和join直到完成。
             */
            invokeAll(new RecursiveActionDemo(source, start, split, dest), new RecursiveActionDemo(source, start + split, length - split, dest));
        }
    }
}