Just as a note to myself (and maybe Igor wants to copy this into the Help):
To install Java on Ubuntu Linux, simply enter the following three commands into the Terminal app:
sudo add-apt-repository ppa:webupd8team/java -y
sudo apt-get update
sudo apt-get install oracle-java8-installer
This adds another software repository to Ubuntu, but the risk of doing so is quite limited IMHO. It is surely much, much easier than installing it by hand (and – more important – to make it work).
It would be interesting to read about CafeTran's responsiveness on Linux. My guess would be that it resembles that of OS X, since Linux is really multi tasking too.