Sun Java moved to the Partner repository
For ubuntu-10.04-lts, the sun-java6 packages have been dropped from the multiverse section of the ubuntu archive. it is recommended that you use openjdk-6 instead.
If you can not switch from the proprietary Sun JDK/JRE to OpenJDK, you can install sun-java6 packages from the Canonical Partner Repository. You can configure your system to use this repository via command-line:
add-apt-repository "deb http://archive.canonical.com/ lucid partner" |
then
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner" sudo apt-get update sudo apt-get install sun-java6-jdk |