private synchronized void sampleLockUsage() {
    final ReentrantLock lock = lockToMonitor.get();
    if (lock != null) {
      final boolean isLocked = lock.isLocked();
      final int queueLength = lock.getQueueLength();
      final int competingThreads = queueLength + (isLocked ? 1 : 0);
      competingThreadsHisto.recordValue(competingThreads);
    }
  }
private synchronized void sampleLockUsage()