详解JDK中ExecutorService与Callable和Future对线程的支持

1、代码背景：

假如有Thread1、Thread2、Thread3、Thread4四条线程分别统计C、D、E、F四个盘的大小，所有线程都统计完毕交给Thread5线程去做汇总，应当如何实现？

2、代码：

统计“盘子”大小的代码，此处实现jdk中的Callable接口，

package com.wang.test.concurrent; import java.util.concurrent.Callable; public class Task1 implements Callable<Integer> { private int x; private int y; public Task1(int x, int y) { this.x = x; this.y = y; } @Override public Integer call() throws Exception { return x*y; } }

统计汇总的代码，也是实现jdk中的Callable接口，

package com.wang.test.concurrent; import java.util.concurrent.Callable; public class Task2 implements Callable<Integer> { private int x; private int y; private int q; private int w; public Task2(int x, int y, int q, int w) { this.x = x; this.y = y; this.q = q; this.w = w; } @Override public Integer call() throws Exception { return x + y + q + w; } }

客户端：使用JDK中Executors.newFixedThreadPool方法创建ExecutorService，ExecutorService的submit方法接收Callable接口的实现，JDK内部将弄成线程处理，使用Future接收submit方法的返回值，当future调用get方法时，如果线程还没有执行完，程序阻塞在这里，知道线程执行完。

package com.wang.test.concurrent; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; public class Client { public static void main(String[] args) throws Exception { ExecutorService pool = Executors.newFixedThreadPool(4); Task1 t1 = new Task1(1,2); Task1 t2 = new Task1(23,34); Task1 t3 = new Task1(23,456); Task1 t4 = new Task1(3,33); Future<Integer> f1 = pool.submit(t1); Future<Integer> f2 = pool.submit(t2); Future<Integer> f3 = pool.submit(t3); Future<Integer> f4 = pool.submit(t4); //Future调用get方法时，如果线程还没有执行完，程序阻塞在这里 Task2 t5 = new Task2(f1.get(), f2.get(), f3.get(), f4.get()); Future<Integer> f5 = pool.submit(t5); System.out.println(f5.get()); pool.shutdown(); } }

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