is there a java library which can handle quaternions and matrices (quaternion matrix multiplication) with all the standard operations?
(i searched google and here before - but didnt find any adequate solution)
The Jave3D javax.vecmath package has quaternions support (Quat4D) and quite a lot of the most common operations are supported. It also has matrix operations that can be applied to quaternions.
You will probably find that it fits most of your needs - and it should not be too hard to add any additional operations if you need them.