@Override
  public ReentrantReadWriteLock getLock(T id) {
    lockPool.purge();
    ReentrantReadWriteLock readWriteLock = lockPool.get(id);
    return readWriteLock;
  }
Get the ReentrantReadWriteLock corresponding to the given id
@param id an arbitrary number to identify the lock
hbase-server/src/main/java/org/apache/hadoop/hbase/util/IdReadWriteLockWithObjectPool.java