translate java code into fsm

I am trying to build up a tool that can translate RSA Java source code to a model called FSM ( finite state machine) by using antler and java parser, RSA is RSA an asymmetric cryptography algorithm. The process should be as translating the source code into AST, then AST to FSM. The input it is the java source code itself, where the output should be the FSM model. I hope was able to explain better. If any other questions, let me know.