The 6.06 Dapper release includes support for Sun JVMs via the Multiverse repositories. Add support for multiverse to your /etc/apt/sources.list

deb http://pa.archive.ubuntu.com/ubuntu/ dapper multiverse deb-src http://pa.archive.ubuntu.com/ubuntu/ dapper multiverse

Do a standard sudo apt-get update , followed by a sudo apt-get install sun-java5-jdk .