1、需求

把计算分批交给多个不同子线程进行暂时异步并发计算，最终主线程汇总计算结果。

2、示例代码

package javabasic.thread;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;

public class CallableWaitDemo {
    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newFixedThreadPool(5);
        Integer num = 10;
        List<FutureTask<Integer>> list = new ArrayList<>(num);
        for (int i = 1; i <= num; i++) {
            FutureTask<Integer> task = new FutureTask(new MyCallable(String.valueOf(i),1000, i));
            //new Thread(task).start();
            threadPool.submit(task);
            list.add(task);
        }

        Integer sum = 0;
        for (FutureTask<Integer> v : list) {
            try {
                sum += v.get();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }

        Integer verifySum = 0;
        for (int i = 1; i <= num; i++) {
            verifySum += i * 1000;
        }

        System.out.println();
        System.out.println("多线程计算累计总和：" + sum);
        System.out.println("主线程校验累计总和：" + verifySum);

        if(!threadPool.isShutdown()){
            threadPool.shutdown();
        }



    }
}

3、任务线程类

package javabasic.thread;

import java.util.concurrent.Callable;

public class MyCallable implements Callable<Integer> {

    private String name;
    private Integer s;
    private Integer num;

    public MyCallable(String name, Integer s, Integer num) {
        this.name = name;
        this.s = s;
        this.num = num;
    }

    @Override
    public Integer call() throws Exception {
        System.out.println("线程" + name + " Ready to work");
        Thread.currentThread().sleep(s * num);
        Integer data = s * num;
        System.out.println("线程" + name + " task done,中间结果：" + data);
        return data;
    }

}

输出打印

线程2 Ready to work
线程3 Ready to work
线程1 Ready to work
线程4 Ready to work
线程5 Ready to work
线程1 task done,中间结果：1000
线程6 Ready to work
线程2 task done,中间结果：2000
线程7 Ready to work
线程3 task done,中间结果：3000
线程8 Ready to work
线程4 task done,中间结果：4000
线程9 Ready to work
线程5 task done,中间结果：5000
线程10 Ready to work
线程6 task done,中间结果：6000
线程7 task done,中间结果：7000
线程8 task done,中间结果：8000
线程9 task done,中间结果：9000
线程10 task done,中间结果：10000

多线程计算累计总和：55000
主线程校验累计总和：55000