Java 并发编程之ForkJoin框架

ForkJoinPool()
ForkJoinPool(int parallelism)
ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory,
 UncaughtExceptionHandler handler, boolean asyncMode)

ForkJoinPool forkJoinPool = new ForkJoinPool();
ArraySortTask task = new ArraySortTask(array , 0 , size);
forkJoinPool.submit(task);
task.get();

package com.example.concurrent.forkjoin;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.concurrent.RecursiveTask;

public class Fibonacci extends RecursiveTask<Integer>{
    private int n;
    public Fibonacci(int n) {
        this.n = n;
    }
    @Override
    protected Integer compute() {
        if (n <= 1)
            return n;
        Fibonacci f1 = new Fibonacci(n - 1);
        f1.fork();
        Fibonacci f2 = new Fibonacci(n - 2);
        f2.fork();
        return f1.join() + f2.join();
    }
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        ForkJoinPool pool = new ForkJoinPool();
        for (int i = 0; i< 10; i++) {
            ForkJoinTask task = pool.submit(new Fibonacci(i));
            System.out.println(task.get());
        }
    }
}

package com.example.concurrent.forkjoin;
import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveAction;

public class ArraySortTask extends RecursiveAction{
    final long[] array; final int lo, hi;
    ArraySortTask(long[] array, int lo, int hi) {
        this.array = array; this.lo = lo; this.hi = hi;
    }
    ArraySortTask(long[] array) { this(array, 0, array.length); }
    @Override
    protected void compute() {
        if (hi - lo < THRESHOLD)
            // 少于阀值,使用Arrays.sort 快排
            sortSequentially(lo, hi);
        else {
            
            // 取中间值
            int mid = (lo + hi) >>> 1;
            // 拆分任务
            invokeAll(new ArraySortTask(array, lo, mid),
                    new ArraySortTask(array, mid, hi));
            // 归并结果
            merge(lo, mid, hi);
        }
    }
    // implementation details follow:
    static final int THRESHOLD = 1000;
    void sortSequentially(int lo, int hi) {
        Arrays.sort(array, lo, hi);
    }
    void merge(int lo, int mid, int hi) {
        long[] buf = Arrays.copyOfRange(array, lo, mid);
        for (int i = 0, j = lo, k = mid; i < buf.length; j++)
            array[j] = (k == hi || buf[i] < array[k]) ?
                    buf[i++] : array[k++];
    }
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        int size = 10_000;
        long[] array = new long[size];
        Random random = new Random();
        for (int i = 0; i< size; i++) {
            array[i] = random.nextInt();
        }
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        ArraySortTask task = new ArraySortTask(array , 0 , size);
        forkJoinPool.submit(task);
        task.get();
        for (long a : array) {
            System.out.println(a);
        }
    }
}