Blocks library you mean probably.
Anyway the keyword in general is “Voxel” library.
Cubes in minecraft are not really cubes, but Quads on visible sides only, and only where is free space from “cubes”.
There are also many techniques like greedy meshing or light floodflow or etc for “minecraft worlds”
In JME are ton of libs and ton of started games people were doing. Even one Minecraft Mod with physics.
Simple example is active Mythruna project of Paul.
Anyway this is probably lib you search for:
If you ask about my suggestion, then any lib that can add/remove/update chunks of voxels easly/fast with features like water/physics/etc will be fine. You can even simulate this minecraft “microcubes” just by making smaller chunk version over bigger chunk version.