I searched through every Google search results and wondered why after updating my apt-get source list, installing Java in Ubuntu still did not work out. It turned out that my source list were lacking some sources in it. If doing this command

apt-get install sun-java6-jre sun-java6-jdk sun-java6-plugin

will give you an error that package is not found, go to the source list at

vi /etc/apt/sources.list

and use your text editor to check if these lines are there.

deb http://us.archive.ubuntu.com/ubuntu feisty main restricted
deb http://us.archive.ubuntu.com/ubuntu feisty universe multiverse

If not, add them. Update apt-get again by typing

apt-get update


and then run the same command to install Java 6.

apt-get install sun-java6-jre sun-java6-jdk sun-java6-plugin

Follow instructions during installation. To verify that Java 6 has been installed in your system, type

java -version

This post assumes that you are logged in with an account that has root access. If you do not and you are unable to execute any of these commands, add the command sudo.