使用RecursiveTask执行多个任务

代码demo：

import java.util.concurrent.*;

public class ForkJoinDemo {
    static class RecursiveTaskA extends RecursiveTask<String> {
        @Override
        protected String compute() {
            try {
                System.out.println(Thread.currentThread().getName() + "开始运行：" + System.currentTimeMillis());
                TimeUnit.SECONDS.sleep(3);
                System.out.println(Thread.currentThread().getName() + "结束运行：" + System.currentTimeMillis());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "A";
        }
    }

    static class RecursiveTaskB extends RecursiveTask<String> {
        @Override
        protected String compute() {
            try {
                System.out.println(Thread.currentThread().getName() + "开始运行：" + System.currentTimeMillis());
                TimeUnit.SECONDS.sleep(1);
                System.out.println(Thread.currentThread().getName() + "结束运行：" + System.currentTimeMillis());
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "B";
        }
    }

    public static void main(String[] args) {
        ForkJoinPool forkJoinPool = new ForkJoinPool(2);
        ForkJoinTask<String> futureTaskA = forkJoinPool.submit(new RecursiveTaskA());
        ForkJoinTask<String> futureTaskB = forkJoinPool.submit(new RecursiveTaskB());
        System.out.println("准备打印:" + System.currentTimeMillis());
        System.out.println(System.currentTimeMillis() + ":A=" + futureTaskA.join());
        System.out.println(System.currentTimeMillis() + ":B=" + futureTaskB.join());
    }
}

运行结果：

可以发现任务A和任务B是异步进行的，但是使用了join()方法，最终变成同步返回。