How to run test cases on selected java code from within the same application

I Am developing a tool for research purpose.

Now this tool asks to choose a directory of java code files, which i successfully implemented.

Then the tool asks to choose a directory of test cases in order to run them against the earlier selected java code files. (i need to implement this).

Is this possible to be done in java? if yes how?

Actually this is a very important issue for me and any little help is appreciated.

Thanks.