Target Java version for bots
I'm using 1.8, so I don't think 1.7 would be a problem.
Sorry to hear about your arm, hope it heals quickly.
The more important question is which java version is run by clients of a rumble. If your bot is compiled with newer version and the rumble client runs with older java, it will simply refuse to start a battle with your bot. So you will get your stats slower if ever.
I personally run everything with version 7 of the open jdk.