I'm not sure how much this will help you because it is written in C++ and not java, but my team has successfully created a camera tracking program on the raspberry pi that sends the data to the CRio via udp packets. The code can be found
here (the code used on the raspberry pi is in the raspberry pi folder and the rest is robot code).
To send the integer values to the CRio, we just used a some if statements to convert them to strings, and when receiving the data we converted them back into integers.
I hope this helps. If you have any more questions I will try to respond to them as soon as possible.