Legacy ISAM Access Methods for Java?

GamerGeek asks: "I work for a small company in the Midwest. We have some old products written in Databus / PL/B. In my spare time I have been investigating the idea of rewriting these programs in Java. My main problem is that the programs store data in ISAM (Indexed Sequential Access Method) files. Rewriting everything all at once is not feasible so the data needs to stay in the ISAM files. I am looking for a 100% java solution for reading and updating ISAM files. A Google search does not turn up anything. Is there one out there? Does anyone know the file format / process for reading an ISAM file? I would be willing to write a package myself if I had that information and open source it too."