Why am I getting IllegalMonitorStateException?

Question

I get the following Exception being thrown when I try to unlock an object.

Exception in thread \"Thread-1\" java.lang.IllegalMonitorStateException
    at jav         


        

Answer 1

The documentation is pretty clear:

If the current thread is the holder of this lock then the hold count is decremented. If the hold count is now zero then the lock is released. If the current thread is not the holder of this lock then IllegalMonitorStateException is thrown.

So the thread which is trying to unlock isn't the holder of the lock. We can't tell why you expected it to be the same thread without seeing more of your code.