<p>I'd like to install Java on a Psion 5MX with GNU/Linux 16MB RAM machine, will it be possible?</p>

<p>Unfortunatly, <a href="http://www.java.com/en/download/faq/5000080100.xml" rel="nofollow noreferrer">"KVM must be installed by the manufacturer"</a>.</p>

<p>What I want is to be able to is to write basic Java code, test and sketch simple algorithms. 
Important notes: I don't need the graphic part since I'll only use the console (no graphic server) but this will be inside a Debian.</p>

Please give us more details about the machine, besides the OS and the memory. Also give us details on what you hope to accomplish with Java on such an underpowered machine (Java has some big overhead in embedded places as compared to writing native code).
The answer is maybe. I've seen Java running on a machine with 4MB of RAM, but it was not running Linux (in fact there was no OS at all). Link:
Java on the Nintendo DS