Best way to store worldchunks

How do you suggest I store my world chunks (java)? I currently uses an hashmap with a string as key made by using the chunks x cord + " " y cord. It seems to work fine until I want to rebuild my meshes. When I use hashmap.get(key).rebuildMesh(); It simply throws errors. So if anyone can either give me a tip on how to solve this or recommend me another method that would be great.

Don't use java.

Then what should I use? I want to run it cross-platform (desktop), so what else?

>>3
You even have better languages that run on JVM.

How do you suggest I store my world chunks

that feel what i have no world chunks ;_;

I don't know how Minetest does it, but it certainly processes the world in chunks. The Minetest engine is written in C++ and the game logic is done in Lua http://minetest.net/

>>1
Notch? Is that you?

>>7
No.