"How to install J2SE Runtime Environment (JRE) with Plug-in for Mozilla Firefox
* Read #General Notes
* Read #How to add extra repositories
sudo apt-get install sun-java5-jre sun-java5-plugin
* When asked, agree with DLJ license terms.
* To configure J2SE as the default JVM (necessary for programs such as Frostwire, RSSOwl and as a plugin for Mozilla Firefox):
sudo update-alternatives --config java
Then choose the option that corresponds to J2SE."
http://easylinux.info/wiki/Ubuntu_da..._v5.0_Update_8