Java Lock interface and synchronized use note--java thread (third edition)

In Java, the lock that follows the Synchronized keyword is freed when the thread leaves the range of the synchronization block, even if it is out of scope because of an exception. Therefore, when using the synchronized keyword in Java, the exception causes the deadlock to occur without releasing the lock, which never occurs.

Lock Interace in place of the synchronized keyword, Java is not likely to know the scope of this explicit lock, if encountered an exception, this lock holds the locks are not automatically released, easy to lead to deadlock phenomenon. There is an easy way to solve this problem: we can use the Java finally clause to make sure that lock is released when it is finished, regardless of how the method left it.

Java Lock interface and synchronized use note--java thread (third edition)