My mobile Java application won’t run on all Java-enabled phones?

I thought Java is suppose to be write once and run anywhere, why on earth won’t it run on all mobile phones that support mobile Java? At some point while you’re learning to create your own J2ME software, you will probably need to find out which mobile phone your midlet software will run on.

Creating a mobile Java software has its challenges and one of the is trying to get a list of mobile phones that will support the features you plan to have on your mobile application or mobile game. The length of the mobile phone list will greatly depend on the list of features that your application is using.

Obviously not all mobile phones are created equal. For instance, some mobile phones have bluetooth while others don’t. Or some have a GPS module and other mobile phones don’t. Your application’s ability to use this feature will depend on whether the Java platform on that mobile phone has support for a certain JSR.

What’s a JSR or Java Specification Request? To explain it as simple as possible, it’s a specification of an API that will enable your Java mobile software to use a certain feature of a given mobile phone. There are different JSR’s. For instance JSR 82 provides the API for using the bluetooth on a mobile phone while JSR 179 provides an API for location-based functions that allow you to determine the physical location of a mobile phone.

Since not all mobile phones have bluetooth or a GPS if you plan to use those features on your mobile Java software, you will have to get a list of mobile phones where your J2ME software will run.

Which mobile phone support which JSR? Good question. Same question came to me. I initially had the idea of compiling an exhaustive list of all mobile phones and their supported JSR’s. Before doing it, I did a quick Google ‘coz I’m sure people will need such a list and chances are somebody is already maintaining one.

Here’s where I found one. The people at Enough Software in Germany is actually already maintaining one such list. You can find the database with an interactive search page at J2ME Polish. For example to here’s a link to all mobile phones in their database that supports JSR 82.

There’s more than 700 mobile phones on the list and if you want to help update the list you can install a J2ME application that they have created on your mobile phone to save it’s configuration. You can then upload the data into their database to help in creating the current list.

So if you might need to get a list of which mobile phones support a specific JSR just go to the J2ME Polish web site. Better yet help them maintain the list by including information about your mobile phone if it’s not yet available on the database.

If there’s any other site that you know of that maintains a similar list, please post it here as a comment providing the link to the site to help other mobile developers. Thanks.