Major Description
The notes about NIOFileLocker being deprecated due to unreliability have an obvious cause – locks it grabs have already been released before the tryLock method has even exited due to the finally block closing the file descriptor on which the lock is held!
(flock() or fcntl()-based locks, into one of which categories those created by NIO fall on modern Unixlike operating systems, are implicitly closed whenever the file handle on which they're held exits. This is highly desirable behavior, because it means that a lock is implicitly cleared on unclean shutdown of any sort – power failure, SIGKILL to the JVM, etc; this behavior is also perhaps the primary reason to prefer NIO locks to the approach taken by CreateFileLocker).