Use ReetrantLock and Condition to instead of "synchronized, wait, notifyAll".

In this patch, I use ReentrantReadWriteLock and Condition to refactor the implementation.

I wonder why you lock all methods in this new patch. Doesn't this produce additional overhead? E.g. calls to enter() and leave() don't need to be locked. We even don't need to use an AtomicInteger as they are only called inside of synchronized blocks in TypeInfo.

yes, you are right, some locking are not necessary now, they produce some additional overhead. Why I lock all methods, I have some consideration as follows:
(1) I think all the fields in the ObjectLock should be protected by only one lock (not two locks), this will make the code more understandable.
(2) I'm considering to remove the synchronized(locks) in the TypeInfo, and this may be a bottleneck. This will need some other methods in ObjectLock protected by the lock.

I'm not sure about (2) now. I think you are right. I should just protected the methods as same as the 'synchronized' now. So I create a new patch for this.

Final patch