lock.lock() before try [duplicate]

Question

Is there any difference between:

private Lock lock = new ReentrantLock(true);  public void getIn (int direction) throws InterruptedException {       lock.lock();      try {          ... 

and

...  public void getIn (int direction) throws InterruptedException {        try {           lock.lock();           ... 

Compilation goes smoothly and also the program works (I mean the same output)

Should I put lock.lock(); before or after try?...

Thanks for any help

Answer 1

Assuming that lock is a ReentrantLock, then it makes no real difference, since lock() does not throw any checked exceptions.

The Java documentation, however, leaves lock() outside the try block in the ReentrantLock example. The reason for this is that an unchecked exception in lock() should not lead to unlock() incorrectly being called. Whether correctness is a concern in the presence of an unchecked exception in lock() of all things, that is another discussion altogether.

It is a good coding practice in general to keep things like try blocks as fine-grained as possible.

Answer 2

If case No 1, in finally you can just say unlock(). In case No2 you need to check if you are holding the lock before unlock(), otherwise you can get IllegalMonitorStateException