First, sorry for my english.
I may not be very active but i didn’t logged here for many months and paused my game coding for a while, i’m still new and a beginner in game development. As of now i keep on practicing 3d modeling on blender for my assets (because i’m bad at art). Just wanted to ask 
. And also i dont have any idea how to implement minimap. And lastly Hello to everyone.
Hi and welcome back, 
Regarding minimap, maybe your gui framework can handle it.
Or it can be done with a viewport.
Or render to texture → draw to screen.
You can also search these forums plenty of topics on it.
its opensource, so it will stand almost forever. until someone will make other good open source java based 3d engine, but i dont think so. some people always prefer opensource, where they also dont need to pay high TAX for using engine
about minimap: like above 
about blender:
use 2.8 beta blender and export to .gltf, its a best way.
here is 2.8 nice feature:
