the easiest way is to make a sphere in some program like 3dmax and then export it to m3g file and use in your program, there are no any functions generating spheres etc, m3g is only the esential of 3d implementation for mobiles phones, so only the most important classes are aded, for m3g file use go here:
http://fivedots.coe.psu.ac.th/~ad/jg/m3g45/index.htmltheoreticaly you could use some some own implementation of function that makes sphere using some mathematics model, search in google for such implementation
i have not use java3d but if you found this kind of class for generating spheres, try to investigate how it is made and you wil have what you want