countdownlatch 计数锁存器

public class  {
     public static void main(String[] args) {   
         final CountDownLatch latch = new CountDownLatch(2);
         new Thread(){
             public void run() {
                 try {
                    Thread.sleep(3000);        
                    latch.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
             };
         }.start();
         new Thread(){
             public void run() {
                 try {
                     Thread.sleep(3000);
                     latch.countDown();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
             };
         }.start();
 
         try {
            latch.await();
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
     }
}