That's not good, anytime in the future before you install any software put the -s option in the line to simulate the install (apt-get -s install < package >) that way you can test what will happen during install and not install if it will cause problems.

You should not have had to re-install you could have just commented out the line in the sources.list and changed the j2re line in the package database to purge then update and upgrade or dist-upgrade with apt to get back where you were.