Java on PDA's [Archive] - Thoughts Media Forums

Menneisyys

06-21-2005, 05:23 PM

I intend to buy a PDA but got ne suggestions on which kind would suit what I'm doing. I'd prefer 2cop out and use Pocket PC as I've only ever used Windows.

Well, none of the two non-phone-centric mobile platforms are well-equipped with real JVM's. Symbian, Nokia's being committed to Java, is another question - any Symbian-based (or, for that matter, simply J2ME-compliant - even the dirt-cheap Sony-Ericsson T610 or the Motorola T720) phone will run your midlets.

Of the two 'real' PDA op. systems (Palm vs PPC), I'd choose a Pocket PC if you don't need anything fancy; for example, JDK 1.4/1.5 support. If you do need JDK 1.4/1.5 support, then, you may be in problems: so far, I haven't made to make any of the Pocket PC JVM's truly 1.4/1.5-compliant. This, however, doesn't mean they can't be made 1.4/1.5-compliant - it's just that I didn't have the time to find out which Java classes to overwrite in, say, the CrEme 4.0b class library to keep it working but also enable to use 1.4/1.5 java.* (that is, system) classes. This means you will need to stick to either notebooks or Linux-based handhelds (Zaurus etc) if you plan to use current JDK's and/or J2EE.

As you're referring to J2ME (and not fully-fledged JDK 1.4/1.5), however, I don't think you'll have any problems. There're several J2ME-compliant JVM's for the PPC (some of them, like the IBM J9 (http://www.pocketpcthoughts.com/forums/viewtopic.php?t=36013), even support CDC1.1/J2ME2.0), so, you'll be able to run your midlets right on your PDA.

You can even develop (edit and compile) Java on your Pocket PC. As midlets, however, require using the desktop tool 'preverify' to pre-verify class files, it may be impossible to be developed on the PPC. I'm not sure about this and will check it some time. Prolly I find a way for doing the pre-verifying on the PPC too.

Also what would I need to start writing such an application? Do I need 2install J2ME on my PC?

You'll need to install both JDK (Java Development Kit - J2SE SDK), available at http://java.sun.com/products/j2se and the MIDP (Mobile Information Device Profile), available at http://java.sun.com/products/midp , in order to be able to compile, pre-verify and test midlets on your PC.

How will the PDA recognise the Java? Do I need a java plug-in? Is such a thing available for PDA's?

Midlets - if we stick to them and don't speak of generic Java applications/applets - require special running environments. They, therefore, can't be run in a web page. Therefore, you don't need any plug-ins - they're only for applets.

I've tried searching the web but all I get is commercial sites selling JVM's. Will every1 who wants to download my application need to pay for this too.

Unfortunately, Sun has abandoned Pocket PC users by not providing us a decent, and as with other platforms, free runtime environment for the PPC. Sun started to develop a Personal Java JVM for WinCE back in, AFAIK, 2000, but then, the project was closed and the beta pulled from Sun's site - it's not available any more. This was a strategic mistake on Sun's part - a lot of people have turned away from Java and moved to Microsoft's .NET CF. I feel really sorry for Sun for doing so - I have always liked Java as a language and have even posted thousands of Java-related posts into Usenet Java newsgroups back in 1998-1999, and have lead numerous Java training courses (mostly SL-110 and SL-276 courses for the initiated, with some J2EE courses :) ). This means I'm really committed to Java. This is why it certainly frustates me that Sun is ignoring WinCE people and developers.

This all means your users will need some kind of commercial environment to run your midlets in.

Feel free to ask more questions. You may also want to have a look at the thread on compiling Personal Java/ standard Java/applets on the Pocket PC (http://www.pocketpcthoughts.com/index.php?action=expand,40880).