OS/2 and eCS have a few choices when it comes to running Java apps.
You can use the IBM JRE, the GoldenCode JRE, or the Innotek JRE. Unfortunately, all of these choices are far behind the state of the art when compared to the reference implementation: Sun's JRE. Innotek's JRE is the most advanced of the three, being at 1.4.2_09.
Innotek has another interesting property: it is not a port of Sun's JRE, rather it is an adaptation of the Odin toolkit (Odin is OS/2's WINE) able to run a particular incarnation of the Windows JRE.
Michael Holzapfel experimented with a few more recent JREs, and found out that you can actually run Windows' JRE v1.5.0_07 using Innotek's Odin toolkit.
There is a thread on OS2world.com regarding applications that run with this "hacked" JRE.
