当我尝试CountDown时Synchronize被阻塞

Question

我使用CountDownLatch跟踪了the advice I found in this post，我遇到了一个问题。我写了这个测试并运行它，我的线程在尝试同步锁时创建了块。

  private CountDownLatch lock = new CountDownLatch(1);

  @Test
  public void testBlock() {
    Runnable r = new Runnable() {
      @Override
      public void run() {
        try
        {
          synchronized(this) {
            this.wait(50);
          }
        }
        catch (InterruptedException e)
        {
          e.printStackTrace();
          throw (new RuntimeException(e));
        }
        releaseLock();
      }
    };

    Thread t = new Thread(r);
    t.setDaemon(true);
    t.start();

    waitOnCallback();
  }

  private void releaseLock() {
    synchronized(lock) { // Thread t blocks here
      lock.countDown();
    }
  }

  private void waitOnCallback() {
    synchronized(lock) {
      try
      {
        lock.await();
      }
      catch (InterruptedException e)
      {
        throw new RuntimeException(e);
      }
    }
  }

为什么这不起作用？

Answer 1

CountDownLatch不是您需要同步(即删除synchronized(lock)块)的对象。所有线程安全都在对象本身内部处理。