This might not be jme3 related, but what is a better place to ask than between game devs? 
Are there any fast noise libraries for java? I’ve seen libnoise port, but it is virtually impossibile to use for real-time, since delays are ~1 minute.
Like, Perlin noise? What is “fast”?
My IsoSurface stuff has a PerlinNoise class:
https://code.google.com/p/simsilica-tools/source/browse/trunk/IsoSurface/src/main/java/com/simsilica/iso/fractal/PerlinNoise.java
How much noise are you generating where the delays are a minute? Using a noise function like this: http://mrl.nyu.edu/~perlin/noise/ should be fast enough if you are generating a reasonable amount. Even with 12 octaves of that noise used in a fractal I have seen usable framerates. Worst case scenario is you end up running the noise generation in a separate thread. If you are truly generating huge amounts of noise (24+ octaves of noise for a 512x512 heightmap) then I recommend putting the calculations on the GPU.
This delay was mostly because of libnoises slow speed. I’m generating few types of noise each about 8 octaves and mixing them together. 512x512 is minimum