I'm currently working on this Java on ARM (Android running Linux) for multiple distributions; Ubuntu included. I am curently running Debian Squeeze, by way of the Debian Kit app, ontop of Android.
You can find all the notes and links that I've complied about this subject in the attached link to the XDA thread that I maintain; my user name for XDA is S0AndS0. Feel free to contact me to either help with the effort or post questions about my methods. I will be writing and maintaining a collection of scripts and quick mods for those that are running Linux on mobile devices which I'll eventually release on the Android Market Place as a "Companion to Linux" app, for making all our lives a little easier.
[Guide] Debian Kit & Limbo PC Emulator (QEMU x86) for Dual-booting Linux on Android
I mantain a github account under the same user name S0AndS0 and you can find a fully working scripted expereance that will; download java jre hard float, jre soft float, JDK hard float, JDK soft float; Install either JDK flavors (still working on jre installers) after download is compleated; and give options to download java dependent software to test if it works. To run the main script; open a terminal window and input the following commands~
git clone https://github.com/S0AndS0/Debian-Kit-Mods
~choose option 1 when prompted to unpack the download script and if you want a scripted install expereance choose option 4 within that script for JDKsf or test option 3 for JDKhf and you'll then eventually be prompted by the installer script (mostly yes to continue prompts) be sure to read what you're saying yes or no to. And in ruffly 20-40 minuets you'll have Java from source installed to your ARM Linux OS.
Update 03042014- edited above for easier reading and removed information that is now outdated dew to script updates, now only requires 2 command line commands and a few prompts to download and install Java's JDK hard or soft float. Now looking for testers to test the hard float version.