public final void awaitTerminated() {
    monitor.enterWhenUninterruptibly(isStopped);
    try {
      checkCurrentState(TERMINATED);
    } finally {
      monitor.leave();
    }
  }

  @Override
  public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException {
    if (monitor.enterWhenUninterruptibly(isStopped, timeout, unit)) {
      try {
        checkCurrentState(TERMINATED);