Install sun-java6-jdk on Ubuntu 10.04

I just had trouble to install the Sun Java6 JDK after updating to Ubuntu 10.04. The problem was that the system couldn’t find the package sun-java6-sdk and apt-get gave me the message:

Package sun-java6-jdk is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package sun-java6-jdk has no installation candidate

What I did to solve this problem was to add a new source

sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"

After this...

sudo apt-get update
sudo apt-get install sun-java6-jdk

It worked fine for me.