If you want to run Java applications on a Pocket PC, you need to install a Java Virtual Machine (JVM) to manage and run the applications and the Java applications.  I don't know much about Java, but I recently installed two different Java based applications (or MIDlets) to my hw6925 and discovered that the IPAQ hw6900s already include a Java Virtual Machine in their set of preinstalled applications. 

Java Application Manager Software

The JVM that is installed on hw6900s is called Esmertec Java Application Manager Software (AMS).  Esmertec Java AMS enables the Pocket PC to run Java Mobile Information Device applications (aka as MIDlets) which are written in the J2ME Connected Limited Device Configuration (CLDC), Mobile Information Device Profile (MIDP).  Many of the more recent Pocket PCs and Smartphones (those running WM5.0 or above) may include JVMs, so if you don't have an hw6900, review the installed applications on your Pocket PC to see if one is already installed to your device.

If you do not have a JVM already installed on your device, you can review the Java Midlet Bible articles (links posted under the "Additional Reading" section of this article) to find links where you might find a compatible JVM for your device.  I am aware of several free "OEM hacked" JVMs for Pocket PCs and Handango sells a couple of expensive Java Virtual Machines for Pocket PCs.

Java MIDlet applications are deployed in JAR and JAD files:

• JAR files are compressed files that include the application installation files (very similar to a CAB file).  You can view the contents of a JAR file with any zip application.
• JAD files (java application descriptor) contain descriptive information about related JAR files such as the MIDlet name, the MIDlet jar file location, etc.

You can install Java MIDlets from the Pocket PC's Browser, directly from a URL, or by using files that are stored locally on your device.

Tapping Menu > Install > Browser opens Internet Explorer and allows you to navigate directly to a website to install Java applications directly to the Pocket PC.	Tapping Menu > Install > URL > Add opens up a page where you can enter specific website URLs to  retrieve and install Java applications directly to the Pocket PC

Unfortunately most websites that distribute Java applications do not recognize the hw6900 (or any Pocket PC) as being Java capable, so I found it near impossible to retrieve and install Java files directly to the hw6900 using either of these options.  Instead I had to search for and download the JAR and JAD files to my computer.

Once the JAR and JAD files were on my computer, then I could copy them to the Pocket PC and use Esmertec Java's "Local Files" option to install the applications on the mobile device.

Installing a Java application - Opera Mini

The first Java application I installed was Opera Mini, a free light weight browser.  Installing Opera Mini to the hw6900 was easy once I figured out what the Esmertec Java software was and how to use it.  To install Opera Mini to a hw6900:

• Download the "Generic Advanced MIDP2" version of Opera Mini 4.1 to your computer: (Be sure to download both the opera-mini-advanced.jar and opera-mini-advanced.jad files).
• Create an "Operamini" folder on the storage card that you use with your Pocket PC and then copy the JAR and JAD files from your computer to this folder.  NOTE:  You can place these files anywhere except for the \Windows folder or any subdirectories in the \Windows folder.
• Tap Start > Programs > Java icon
• Tap  Menu > Install > Local Files.  The software searches main memory and any installed storage cards for Java files.  NOTE: Esmertec Java will find all MIDlet installation files on the Pocket PC except for any files saved in the \Windows folder or any subdirectories in the \Windows folder.

• Highlight the file you want to install and tap Install.  The software will provide some information about the MIDlet you selected to install.  Tap Continue

• You may receive some warnings that inform you the MIDlet is requesting permissions and asking you if you wish to continue, select the enter button on the keyboard (on the hw6925, the screen does not display a YES or OKAY key). Continue tapping through any additional prompts until you receive confirmation that the software has been installed on your Pocket PC.  

• The screen will indicate that it is "finishing installation." After several moments, you will be asked if you want to launch the MIDlet.

You can also install Java MIDlets by using File Explore to navigate to the JAR / JAD file and tapping the file (similar to the way you would install CAB files to the Pocket PC).  I found that both the JAR and JAD files are needed to install the application through Esmertec Java's Install option. 

When you install MIDlets to your Pocket PC, application files are installed to the \Windows\appdb\ folder.

Running Java Applications

After you've installed the MIDlet to your Pocket PC, you access it by tapping Start > Programs > Java icon > Tap Launch or the application you want to use.

You can uninstall Java applications by tapping Start > Programs > Java icon. Then you can press and hold your stylus on the application and select Uninstall from the popup menu or you can tap Menu > Actions > Uninstall.

Additional Reading

• jeodeko-help.0409.htm: This is a pretty good help file for Esmertec Java that is included on the hw6900.  Look for it in the Windows folder of the hw6900 
• The (Java) Midlet Bible, Part I
• The (Java) Midlet Bible, Part II
• Java on Pocket PC (Unofficial FAQs)

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