This is pretty difficult because C is of much lower level compared to Java. I don't think such work would make any sense. There are products which can be used to compile code written in different languages to Java machine. I used Ada; but it could also be C#, Object-oriented dialect of Pascal, Python, PHP, and more. Please see:
Adding C to this list can hardly do something good. The languages good to target JVM are usually object-oriented, or have close capabilities. You need something to represent classes, members of classes and related encapsulation. This is not about C.
And the term "converting to Java code" sound just ridiculous. What could you possibly mean by that? Listen for a good friendly advice: just forget it.