docs: private boolean tryLockCacheFile()
    {
      int cnt = 0;
      boolean locked = false;
      while (cnt < 100 && !(locked = lockCacheFile()))
      {
        try
        {
          Thread.sleep(100);
        }
        catch (InterruptedException ex)
        {
          // doesn't matter
        }
        ++cnt;
      }
      if (!locked)
      {
        LOGGER.debug("Failed to lock the cache file.");
      }
      return locked;
    }