How do i "Whitelist" my .jar?

So, i'm coding a minecraft launcher which contains a cheat, and this cheat is commerciable, so i want to perm only the persons who bought the client access it.

I pretend to do this adding a whitelist in my launcher.bat/launcher.jar , so when a person launch it, it will check if this nickname is on my whitelist, if yes then proceed to the intializing, if not, automatically closes and send a message like "Insufficient permissions."

Does anyone knows how to do this? If i need to use a .xml with the nicks idk

I think if you want a commerciable cheat you should think about a login system, other than a simple whitelist that can easily be bypassed with a bit of knowledge. Check login credentials somehow via php or something and build in killswitches if login fails too often. Just simple ideas, you can definetly come up with better ones.

If Java is the programming language you're most comfortable with, and you want to build some kind of proper licensing server that you can use I would suggest building a simple microservice with something like Spring Boot. Have a look at https://spring.io/guides/tutorials/rest/ for example.

Very complicated request, realistically speaking if you go for a serious option it will set you back a few hundred dollars and 100s of hours in time spent.

I would begin by obfuscating your content, and creating some kind of web service which can authenticate copies in the wild and send them kill signals if they are unverified. Issue is, java binaries are very easy to reverse and so you will undoubtedly have your code leaked at some point if you don't take it to the Nth degree.