Changing the Default Java Runtime Environment in Ubuntu

I've been having trouble with a couple Java programs in Ubuntu, so I'm attempting to switch the Java Runtime Environment from the OpenJDK, which is default in Ubuntu, to the official Sun runtime. I found instructions, which I've followed with the following changes:

• the partner repository was added through the GUI Software Sources utility (System menu -> Administration -> Software Sources, or from the Ubuntu Software Center, Edit -> Software Sources)
• The sun-java6-jre and sun-java6-fonts packages were installed by searching in the "Canonical Partners" section of the Ubuntu Software Store. The sun-java6-plugin package was not found and not installed.

Here's hoping things improve, and that there are no problems because of not installing the plugin package.