Java父线程(或是主线程)等待所有子线程退出的实例

static void testLock1(){      final AtomicInteger waitCount = new AtomicInteger(30000);   final Object waitObj = new Object();   System.out.println("start"+System.currentTimeMillis());   for (int i=0;i<30000;i++) {    new Thread(new Runnable() {     @Override     public void run() {      try {       Thread.sleep(10);      } catch (InterruptedException e) {       e.printStackTrace();      }      waitCount.decrementAndGet();      synchronized(waitObj){       waitObj.notifyAll();      }     }    }).start();   }   while( waitCount.intValue()>0) {    synchronized (waitObj) {     if(waitCount.intValue()>0){      try {       waitObj.wait();      } catch (InterruptedException e) {       e.printStackTrace();      }     }    }   }   System.out.println("ok"+System.currentTimeMillis());  }  static void testLock2(){      final CountDownLatch workLauch = new CountDownLatch(30000);//计数器   System.out.println("start2"+System.currentTimeMillis());   for (int i=0;i<30000;i++) {    new Thread(new Runnable() {     @Override     public void run() {      try {       Thread.sleep(10);      } catch (InterruptedException e) {       e.printStackTrace();      }      workLauch.countDown();     }    }).start();   }   try {    workLauch.await();   } catch (InterruptedException e) {    e.printStackTrace();   }   System.out.println("ok2"+System.currentTimeMillis());  }  public static void main(String[] args) {   testLock1();   testLock2();  }