java主线程等待线程池所有子线程都结束后在执行的演示代码

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.CountDownLatch;

public class Main {
    private static final int loopNum = 1*10;

    public static void main(String args[]) throws Exception {
        Main TestThreadPool = new Main();
        long bt = System.currentTimeMillis();
        List<String> list = new ArrayList<>();
        list.add("0");
        list.add("1");
        list.add("2");
        list.add("3");
        list.add("4");
        list.add("5");
        list.add("6");
        list.add("7");
        list.add("8");
        list.add("9");
        CountDownLatch count = new CountDownLatch(10);
        TestThreadPool.m1(list,count);
        count.await();
        long et2 = System.currentTimeMillis();
        System.out.println("[1]耗时:"+(et2 - bt)+ "ms");
        Thread thread = new Thread();
        long at = System.currentTimeMillis();
        TestThreadPool.m2();
        long et3 = System.currentTimeMillis();
        System.out.println("[2]耗时:"+(et3 - at)+ "ms");

    }

    public void m1( List<String> list,CountDownLatch count) {
//        ExecutorService pool = Executors.newCachedThreadPool();
        ExecutorService pool = Executors.newFixedThreadPool(4);
        for (int i = 0; i < list.size(); i++) {
            String str = list.get(i);
            System.out.println(list.get(i));
            Runnable run = new Runnable() {
                public void run() {
                    try {
                        new Thread().sleep(1000);
                        //模拟耗时操作
                        System.out.println("[1]" + Thread.currentThread().getName()+"----"+str);

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    count.countDown();
                }
            };
            pool.submit(run);
        }
        System.out.println("[1] done!");
        pool.shutdown();
    }

    public void m2() {
        AtomicInteger connectionIds = new AtomicInteger(0);
        for (int index = 0; index < loopNum; index++) {
            try {
                new Thread().sleep(1000);  //模拟耗时操作
                System.out.println("[2]" + Thread.currentThread().getName());

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        System.out.println("[2] done!");
    }
}