I use Ubuntu 14.04 LTS, 64-bit.
In attempt to run some 32-bit programs, I had to install java version 6. Java version 7 was already present.
I used update-alteratives to switch between them.
Somehow I messed up completely and want to remove all contents of both versions of java and re-install.
I used apt-get remove but I think some parts of java are being left over.