This method fails in the event that the application crashes. All further instances (even a valid one) will think another instance is running.

On the other hand, if you keep the file handle open after creat (something I forgot), no one else will be able to create the file, but if you crash, the O/S should clean up after you.

This doesn't work so well on Windows, because Windows is horrible about trying to clean up after crashed applications.

You are spot on. The problem would arise if the program crashes or if the computer shuts down improperly (in case of power failure).

Well, I have found another workaround. Using sockets is an option. So when the jar (java app) is started, bind it to an arbitrary, high port (high port is to ensure that the port is free and available to be used). When the application exits, close the port. Whenever the application is run, bind it to the same port. So this ensures another instance is not open when one is already running.

Advantage is that it is much easier when compared to the file opening/locking method.

Disadvantage is that the program won't run if the port is already in use. So use a high end port (for ex, 50000 or higher) as the chances of these ports being used are less.