Java on the HP Jornada 720

This is very rough (as is the rest of my site), but I wanted to get it up online as soon as I could so other Jornada 720 users could start using their Jornadas to compile and run Java apps and so perspective Jornada buyers would see that in addition to being the best little PDA on the market, the 720 is also a mini-computer on which you can compile and learn Java.

The impetus for this project was that I began taking a class to learn Java at the local university. I wanted to have Java with me when I was commuting so I could try things out. I also wanted to be able to follow along in class and actually attempt examples along with the professor. I had settled for quite a while on just having a copy of Bruce Eckel's wonderful book "Thinking In Java" (http://www.mindview.net/Books/TIJ/) on my Jornada and just using the Jornada to read the book. That was until I came across a site describing how to compile Java on a Psion 5mx and another post on Deja from a user who claimed to compile Java on an HP Jornada 680.

So I started working with the Psion site (http://www.hasiland.com/javaonepoc/javac.html) and using the instructions there I was able to get Javac running on my 720. Much thanks to Frank Bodmann for coming up with this in the first place for Psion. I simply followed his lead and was able to get it running on mine. And here's how I did it.

• Step 1: Install Personal Java for Windows CE for the ARM processor. This can be found on Sun's site if you register (it's free) for a login on their site. http://developer.java.sun.com/developer/earlyAccess/personaljava/. I installed it on my compact flash card, so in my pictures and examples the path to the Personal Java install will be "\Storage Card\Program Files\Java". One caveat to this install is that it doesn't detect the 720 as an HPC. So after installing Personal Java on the 720 you need to open it using Winzip or another archive program and extract the files named "pjava.002" and "wcecom~1.003". In the Personal Java install folder rename pjava.exe to pjava.exe.old and wcecompat.dll to wcecompat.dll.old. Finally, copy wcecom~1.003 and pjava.002 into the "\bin" directory of your Java install and rename them wceCompat.dll and pjava.exe respectively. Next, use Sun's directions and samples to ensure the Personal Java is working. This can be a bit tricky and usually works best from the command line.

• Step 2: Create a folder to store your class files and .java source files. I chose \Classes because that meant less to type on the command line.

• Step 3: Following the directions on Mr. Bodmann's site I installed the JDK 1.1 on my desktop. Then I used winzip to open lib\classes.zip and extracted the following files and folders.

  sun/tools/asm/*.class
  sun/tools/java/*.class
  sun/tools/javac/*.class
  sun/tools/javac/resources/javac.properties
  sun/tools/tree/*.class
  

  I zipped these into an archive named javac.zip which I then renamed javac.jar and copied to the lib directory of my Personal Java install on my Jornada 720. In my case this was \Storage Card\Program Files\Java\lib.

• Step 4: Next I took the following classes from my JDK 1.1 install (in my case JDK 1.1.8)...

  java/awt/*.class
  java/io/*.class
  java/lang/*.class
  java/net/*.class
  java/security/*.class
  java/text/*.class
  java/util/*.class
  

  ....and wrapped them up like above into a zip file named missing.zip which I renamed missing.jar and placed in the lib directory of my Personal Java install on my 720. Here is a picture of these .jar files in that folder.

  

• Step 5: Next I created my own Javac.java wrapper source file and compiled it on my desktop. You can download the source and class file here. I copied these into my "\Classes\" directory.
• Step 6: That's all there was to it. Now it was just a matter of running Javac.class via Personal Java to compile a .java file. My tactic in doing this has been to use a notepad product to write the .java files, then to use Personal Java to compile and ChaiVM to actually run the output. The reason being that ChaiVM is much more reliable right now at console output. I use the command prompt (cmd.exe or just "cmd" from the run prompt) to run Javac.java. To run it you need to run Javac through the Personal Java virtual machine (pjava.exe) and include in the classpath the .jar files we copied over from earlier. Look in the pictures below for an example of what this command looks like at the prompt.

Below are some more pictures, but please let me know if you have any questions or tips on how to improve this obvious rough draft both of the procedure and the directions.

The .jar files in their new home.
 

The source code for Javac.java.
 

A template file storing the long and difficult command that would have to be typed into the command line each time if I didn't paste it.
 

Now I've pasted this command into my command prompt window and I'm getting ready to use it to run "\Classes\Javac.class" against "\Classes\HelloWorld.java".
 

Here we go compiling.
 

Here's what HelloWorld.java looked like.
 

Now we get ready to run it in ChaiVM by clicking "Browse" and navigating to the "\Classes" directory to find "HelloWorld.class".
 

Now we run it and WOW, it works!