Java runtime environment JRE was moved to the partner repository in Ubuntu , so now if you want to install it you have to do it from the command line.
Open the terminal and add Lucid partner repository using the command :
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
Note : If the command above didn`t work for you, just retype the quotations "" and will work for you.
Refresh the sources list
sudo apt-get update
Read more: LinuxTree