To get java (you'll also get geany and you'll need a working internet connection ) type the command in mate terminal:
sudo apt-get install -y openjdk-7-jdk geany
It will take some time depending on your internet connection if you get an error report do the command above or check if your internet is working. I hope this advice worked, if not, check out Magpi Issue 14 (the link is raspberrypi.org/magpi/magpi-issues and scroll to the issue with a computer module. That's the issue you want get. Click the name and click download. Open with Antril and scroll to the part with the part that says cup of java.
Hope this advice works.