As already you know, canonical no longer redistribute the Java packages due to license issue. Canonical removed the Java packages from their repository and now they distribute openjdk as alternative,If you need Java on Ubuntu; installation must do through the external repository. Here is the tutorial about installing Oracle Java7 on Ubuntu 11.10.
Open Terminal ( Ctrl + Alt + T ).
Remove the OpenJDK from the system if already you have it installed.
raj@geeksite~/$ sudo apt-get remove --purge openjdk*
raj@geeksite~/$ sudo apt-add-repository ppa:eugenesan/java
Update the repository on your system. Ignore if any error occur.
raj@geeksite~/$ sudo apt-get update
Install Sun Java6 and its plugins. Note: It might verify the installation of packages, type Y to confirm.
raj@geeksite~/$ sudo apt-get install oracle-java7-installer
Verify the installation by visiting the following link.