public int size() {
    lock.readLock().lock();
    try {
      return delegate.size();
    } finally {
      lock.readLock().unlock();
    }
  }
Returns the number of elements in this queue.
@return the number of elements in this queue
hbase-server/src/main/java/org/apache/hadoop/hbase/master/normalizer/RegionNormalizerWorkQueue.java