CountDownLatch startedLatch = new CountDownLatch(1);
    startThread(
        () -> {
          startedLatch.countDown();
          enterSatisfyGuardAndLeaveInCurrentThread();
        });
    awaitUninterruptibly(startedLatch);
  }

  private void enterAndRemainOccupyingInAnotherThread() {
    CountDownLatch enteredLatch = new CountDownLatch(1);
    startThread(
        () -> {
          monitor.enter();

    CountDownLatch startedLatch = new CountDownLatch(1);
    startThread(
        () -> {
          startedLatch.countDown();
          enterSatisfyGuardAndLeaveInCurrentThread();
        });
    awaitUninterruptibly(startedLatch);
  }

  private void enterAndRemainOccupyingInAnotherThread() {
    CountDownLatch enteredLatch = new CountDownLatch(1);
    startThread(
        () -> {
          monitor.enter();

     * and extracts child URLs until the crawling process is done or no more URLs are available.
     */
    @Override
    public void run() {
        log(logHelper, LogType.START_THREAD, crawlerContext);
        int threadCheckCount = 0;
        // set urlQueue to thread
        CrawlingParameterUtil.setCrawlerContext(crawlerContext);
        CrawlingParameterUtil.setUrlQueueService(urlQueueService);