package com.smart.thread;

import java.util.Date;
import java.util.concurrent.CountDownLatch;

/**

• Java多线程编程中经常会碰到这样一种场景——某个线程需要等待一个或多个线程操作结束（或达到某种状态）才开始执行。

• 比如开发一个并发测试工具时，主线程需要等到所有测试线程均执行完成再开始统计总共耗费的时间，

• 此时可以通过CountDownLatch轻松实现。

• Created by jinxiaoyu on 17/4/11.
  */
  public class CountDownLatchDemo {
  public static void main(String[] args) throws InterruptedException {
  int totalThread = 3;
  long start = System.currentTimeMillis();
  final CountDownLatch countDown = new CountDownLatch(totalThread);
  for(int i = 0; i < totalThread; i++) {
  final String threadName = "Thread " + i;
  new Thread() {
  @Override
  public void run() {

               System.out.println(String.format("%s\t%s %s", new Date(), threadName, "started"));
               try {
                   Thread.sleep(1000);
               } catch (Exception ex) {
                   ex.printStackTrace();
               }
               countDown.countDown();
               System.out.println(String.format("%s\t%s %s", new Date(), threadName, "ended"));
           }
       }.start();
   }
   countDown.await();
   long stop = System.currentTimeMillis();
   System.out.println(String.format("Total time : %sms", (stop - start)));
  

  }
  }

Tue Apr 11 21:29:07 CST 2017 Thread 2 started
Tue Apr 11 21:29:07 CST 2017 Thread 0 started
Tue Apr 11 21:29:07 CST 2017 Thread 1 started
Tue Apr 11 21:29:08 CST 2017 Thread 2 ended
Tue Apr 11 21:29:08 CST 2017 Thread 1 ended
Tue Apr 11 21:29:08 CST 2017 Thread 0 ended
Total time : 1049ms