1、countDownLatch定义：它是java并发包里的，所以它肯定是用于java并发的场景；
2、它的主要方法就几个：
CountDownLatch(int count) //实例化一个倒计数器，count指定计数个数；
countDown() // 计数减一
await()；等待计数器到0，然后所有线程同时执行；
3、所以我使用它的一个场景就是模拟大量的并发请求，直接上代码：
@Service
public class InitThreadService {
private static final Logger log = LoggerFactory.getLogger(InitThreadService.class);
private static final int ThreadNum = 1000;
@Autowired
private ConcurrentService concurrentService;
public void generateThread () {
log.info("开始初始化线程，线程数量为：" + ThreadNum);
try {
CountDownLatch countDownLatch = new CountDownLatch(1); //计数器
for (int i=0; i<ThreadNum; i++) {
new Thread(new newThread(countDownLatch)).start();
}
//等线程创建完毕后，计数器归零；
countDownLatch.countDown();
} catch (Exception e) {
log.info("初始化线程失败：" + e.fillInStackTrace());
}
}
public class newThread implements Runnable {
private final CountDownLatch startLatch;
public newThread (CountDownLatch startLatch) {
this.startLatch = startLatch;
}
@Override
public void run() {
try {
startLatch.await();//线程都等待在这里
log.info("线程开始干活了：" + System.currentTimeMillis());
concurrentService.manageRobbing();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}