1.) Uncomment  main-restricted and universe. Open Adept from the start menu in System. In Adept menu select Manage Repositories. Once uncommented click Fetch Updates. While you're there uninstall the default free java that is installed by default.

2.) Open the terminal and install Java 6 packages using apt-get:

$ sudo apt-get install sun-java6-bin sun-java6-jdk sun-java6-jre sun-java6-plugin

3.) Edit bash_profile

$ sudo kate .bash_profile

Add java (/usr/lib/jvm/java-6-sun/jre/bin) to your path, should look similar to the following:

# set PATH so it includes user's private bin if it exists
if [ -d ~/bin ] ; then
    PATH=~/bin:/usr/lib/jvm/java-6-sun/jre/bin:"${PATH}"
fi

Add the following to the end of your bash_profile file:

export JAVA_HOME="/usr/lib/jvm/java-6-sun"

Exit the terminal and do ctrl+alt+backspace

4.) Adding java-plugin to Firefox.

Open a terminal:

$ cd /usr/lib/mozilla-firefox/plugins
$ sudo ln -s /usr/lib/jvm/java-6-sun/plugin/i386/ns7/libjavaplugin_oji.so ./libjavaplugin_oji.so

if you use mozilla cd to /usr/lib/mozilla/plugins instead.