I doubt that many people here know how to debug JFreeChart. I would suggest that you post your question to the JFreeChart support forum.
I couple of points before you go:
* If your question has to do specifically with the Java language, then yes, post it here.
* When you post code, please include the import statements. That helps us understand what is your code and what is some third-party's code.
All things are lawful, but not all things are profitable.