Structs to classes

I have been given the task creating a java application that mimicks a C app that we want to replace. The problem is that the old C app uses a lot of structures that have other structures as data members, there's even some unions. Instead of recreating all these structures in classes I was wondering if anybody knew how to import or use them in native mode? This is just for a proof of concept to prove that we can do it, so I'm not too worried about performance right now. If the project is approved we'll recreate the structures in java. Sample code is appreciated. Thanks.

Andy