Restrict multiple instances of an application in java

Question

I want to prevent multiple instances of application being launched in java. I know 2 methods for this:

1. locking file
2. locking socket

But

Answer 1

I know that this question is pretty old, but I have to solve the same problem at the moment. I prefer the socket solution because I have never thought that such kind of task should have anything to do with the file system. It is better to solve the problem in memory and not in the file system I think.