java为什么无法检查当前线程是否持有ReentrantReadWriteLock的读锁？

Question

我发现ReentrantReadWriteLock的写锁提供了一个isHeldByCurrentThread()方法来检查调用线程是否持有该锁

但是对于读锁没有相应的isHeldByCurrentThread()方法。为什么不呢

Answer 1

我想答案就在Doug Leas对这个问题的评论中：http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6207928

Doug Lea写道：

The current design and behavior are intentional. Read-locks are normally not defined to have a notion of ownership, so ownership cannot be tested. … The JSR166 EG has received a few requests to optionally support per-thread read-hold tracking. Doing this would significantly increase lock overhead, so would need to be governed by an optional construction parameter. We are looking into it.

Answer 2

可重入写回。getReadHoldCount（）似乎可以完成这项工作