Installing a Java Midlet Manager on the Treo 750

The Treo 750 does not include a Java Emulator.  Also known as a Java MIDlet Manger, a Java emulator allows you to run programs written in Java for Mobile phones such as Opera Mini.  Most mobile phones include a Java Emulator.  Windows Mobile does not include a built in Java emulator, but most Windows Mobile Pocket PC phone manufacturers include a 3rd party Java emulator pre-installed.  For some reason Palm did not include a Java emulator with the Treo 750.

As of now, these are the two best different Java emulators you can download and install on any Windows Mobile Pocket PC, including the Treo 750:

1) Residoro's Inetent Java MIDlet Manager

Download Here: XDA-Develoers.com forum post (ZIP file)
Or click HERE to download the .CAB file directly from this site.

Intent Java MIDlet manager is produced by Tao Group.  It is included as an OEM application on some Windows Mobile Pocket PC phones, and on all WM5 phones made by HTC (such as the Cingular 8525 for example.)  But Intent is not for sale directly to consumers.
Residoro at XDA-Developers.com extracted the Inetent Java MIDlet manager from the ROM of an HTC Wizard and put it in to an installable .CAB file.  You can download and install it to your Treo 750 to add Java support.

2) IBM WebSphere Everyplace Micro Environment MIDP 2.0 Java Emulator

IBM MIDP 2.0 Java Micro Environment is a Java emulator for mobile devices.  IBM has a version for many operating systems including WM5 Pocket PC.  You can download and install it for free.  The problem with this is that it's a relatively complicated download and install process.  You must register, download it, run the self extracting .exe file on a PC, unzip a file that is installed, then copy the contents of two directories from the unzipped contents directly to the phone.  From there you have to created your own launch shortcut (icon) and associate the Java .jad and .jar files manually with a registry editor.  The instructions on how to do this are in a .PDF file that you can get when you download the software from IBM.

Which One is Better?
Intent Java MIDlet Manager is the best of all available Java emulators.
This article by Smartphone & Pocket PC Magazine sums it up the best.

Regarding using it with Opera Mini, which is my primary reason for installing Java, here are my experiences:

Opera Mini on Intnent Java MIDlet Mangager:
Opera Mini generally works best with this version of Java.
The Windows soft keys also work with Opera Mini's menus.
Intent seems to use less system resources.
However, I have experienced some bugs in Opera Mini while running under Intent.
I experience problems with entry of information on some web sites.  I get error messages when selecting check boxes and radio buttons.  I also am unable to edit/enter text on some text entry fields on some web sites.

Opera Mini IBM WebSphere MIDP Java:
Opera Mini also works great under IBM.
The Windows soft keys do NOT work with the Opera mini menu buttons.  Instead the "Q" key and "P" keys on the keyboard act as left and right soft keys with Opera Mini.  So you still get a keys mapped to the menus, just not the actual device soft keys.
IBM Java seems to use more system resourcs.
I have not experienced any bugs like I do with Intent.  For the most part it works flawlessly.

Conclusion:
The errors I experience under Intent Java are a real showstopper for me.  As a result I use IBM Java because I don't experience these errors.  Otherwise Intent appears to be a better Java emulator overall and might be a better solution if you aren't using Opera Mini.

More tips, see:
http://www.ppcgeeks.com/gmail-gmaps-java-application-tutorial-update-11-21-t1198.html