/**

      * CountDownLatch用法

      * CountDownLatch类位于java.util.concurrent包下，利用它可以实现类似计数器的功能。比如有一个任务A，

      * 它要等待其他4个任务执行完毕之后才能执行，此时就可以利用CountDownLatch来实现这种功能了

      */

     @Test

     public void getThread(){

         final CountDownLatch latch = new CountDownLatch(2);

         new Thread (){

             @Override

             public void run() {

                 try {

                     System.out.println("子线程"+Thread.currentThread().getName()+"正在执行");

                     Thread.sleep(3000);

                     System.out.println("子线程"+Thread.currentThread().getName()+"执行完毕");

                     latch.countDown();

                     System.out.println(latch);

                 }catch (InterruptedException e){

                     e.printStackTrace();

                 }

             }

         }.start();

         new Thread (){

             @Override

             public void run() {

                 try {

                     System.out.println("子线程"+Thread.currentThread().getName()+"正在执行");

                     Thread.sleep(3000);

                     System.out.println("子线程"+Thread.currentThread().getName()+"执行完毕");

                     latch.countDown();

                     System.out.println(latch);

                 }catch (InterruptedException e){

                     e.printStackTrace();

                 }

             }

         }.start();

         try {

             System.out.println("等待2个子线程执行完毕...");

             latch.await();

             System.out.println("2个子线程已经执行完毕");

             System.out.println("继续执行主线程");

         }catch(InterruptedException e){

             e.printStackTrace();

         }

     }