If you're asking this question, I would recommend reading about java first. Since we'll all know what your server will be like. The next L33chScape.
One thing that's nice about programming is that you actually have to think, and use critical thinking skills. You can't be a potato "coder".
Everything about a player is saved in a file whether that's a dat, txt, json, cfg file extension that doesn't matter. It's still doing the purpose of saving information about a player in a file. (Serialization) A characters rights are also stored in this file because it gives us information about a player and his/her rights. Many servers especially PI just use integers to respresent a players rights.
0 = player
1 = player moderator
2 = administrator
3 = owner
4+ can be custom (donator)
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