How to guarantee the uniqueness of an application instance?

Question

Java

Hello. The question is. Let's say I have an application running in the background, App.jar. If I call this jar 4 times, then 4 instances of the same program will hang in my memory, respectively. How can I make sure that only one instance of the program can run at a time?

Answer 1

Lock files, systemd

Answer 2

How about adding a check that looks into processes and looks for a process, and if it's already there, doesn't start a new jar?