主线程等待子线程全部执行完成

实例代码

import java.util.concurrent.Callable;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;public class Demo {    public static void main(String[] args) {        ExecutorService executor = Executors.newFixedThreadPool(10);        for(int i =0 ; i < 20; i++){            executor.submit(new SubThread(i * 1000));        }        executor.shutdown();          try {//等待直到所有任务完成            executor.awaitTermination(Long.MAX_VALUE, TimeUnit.MINUTES);        } catch (InterruptedException e) {            e.printStackTrace();        }        System.out.println("执行完成......");    }}class SubThread implements  Callable<String>{    private long ms;    public SubThread(long ms){        this.ms = ms;    }    public String call() throws Exception {        Thread.sleep(ms);        System.out.println("等待了 --"+ ms+ "ms");        return null;    }}