Need help with RoboRIO <-> Rioduino communications over Serial Ports.

We are having trouble with communications between the RoboRIO and the Rioduino. I have found numerous tutorials on how to connect via I2C in java, and I have found several on connecting via Serial Ports in LabView. Unfortunately, we cannot use I2C and we are using Java exclusively. Does anyone have any experience/advise connecting the two using Serial Ports, in Java?