Installing the Java JDK from the command line is so much easier than Oracle's web package based install.
For ubuntu 10.10, here are the commands:
$ sudo add-apt-repository ppa:sun-java-community-team/sun-java6
$ sudo apt-get update
$ sudo apt-get install sun-java6-jre sun-java6-bin sun-java6-jdk
With ubuntu 11.04 I had to execute these commands:
$ sudo add-apt-repository ppa:ferramroberto/java
$ sudo apt-get update
$ sudo apt-get install sun-java6-jre sun-java6-bin sun-java6-jdk
Set the JAVA_HOME environment variables in your /etc/profile or .bashrc file.
JAVA_HOME=/usr/lib/jvm/java-6-sun
export JAVA_HOME