I’ve been playing around with getting started building Android (I’d like to get 2.0 working on my Joggler). To build Android under Linux, you need the sun-java5-jdk package.
This is due to a conflict in the @Override command, which means you can’t use the Java 6 JDK for this task.
Unfortunately the sun-java5-jdk package isn’t available by default in the Karmic or Lucid repositories, so you need to grab it from somewhere else. To save you searching, here’s the howto: