[Butter's]

Might be because of this?

Thread.sleep(100);

Never used threading for FRC, but I have for game programming. In which my sleep time varies based off a few factors (Another words, it's not just a while loop with a constant sleep time). Not sure how to implement this in FRC, just throwing out the possibility.

Also, you're sleeping for a tenth of a second. Try making the value 1000 (1 second) and see if the usage goes down.

If neither of these work, you might want to use a debugger & pin point what in specific is maxing out the CPU.