I'm assuming that you're talking about the old cRIO's and cRIO II's.
I don't know how to get you enabled with java on those platforms, however this post on WPI may interest you
http://wp.wpi.edu/wpilib/2015/02/05/...ith-old-crios/
Java and C++ are similar enough that you should be able to either switch or at least bridge the gap for now. Certainly better to change languages than to put all those nice cRIOs up on a shelf somewhere to forever collect dust.
Hope this helps