java tutorial for OCC

Dear All,
I'm developing a CAE application using VTK and java.
I have seen that OCC can deal with IGS and STP cad format and so I tried to use occ classes for my application.
It is about one year that I try to understand how to use OCC with java: it is nearly impossible to understand this from the java samples included in occ.
It is necessary to have a step by step tutorial to make occ-java applications: I think that many java developers have been discouraged to use occ for this problem.