Newer the phone, more strange the bug. The following is a bug affecting some Series60 devices (3rd FP1, 3rd FP2 and 5th): Nokia E71, Nokia N79, Nokia N96, Nokia 5800 XpressMusic.

The withespace characters before and after JAD attributes should be ignored according to MIDP specifications but if user tries to install an application with a whitespace character after the last JAD attribute on one of the mentioned decvies he will get a "Compulsory attributes missing".

So, be sure to remove whitespace chars from your JAD!

This issue appears on the Nokia families: Series 80 2nd Edition, S60 2nd Edition FP2, S60 2nd Edition FP3, S60 3rd Edition, S60 3rd Edition FP1.

From Forum Nokia: when a MIDlet tries to edit an existing contact, add a new one, or remove an existing contact using the JSR-75 PIM API on S60 2nd Edition FP2, S60 2nd Edition FP3, and S60 3rd Edition devices, the user is asked for change confirmations every time, even if the API access setting is "always allowed". This includes situations where the MIDlet is placed in the operator/manufacturer domain (excluding S60 3rd Edition FP1 devices), or the user has manually changed the API access settings for the MIDlet in a trusted 3rd party domain.

Unfortunately, there is no workaround for this problem.

Sun is going to announce its own app stores at the Java Conference on 1st of June in San Francisco. According to Sun, Java powers more than 4.5 billion devices, including about 2.1 billion mobile phones and handhelds as well as more than 800 million PCs, 3.5 billion smart cards and myriad set-top boxes, printers, games, car navigation systems and related technologies.

While details on the Java store otherwise remain scarce, it seems that added candidate applications will be submitted via the web, evaluated by Sun for safety and content and presented under free or premium terms to the broad Java audience. "Over time, developers will bid for position on our storefront, and the relationships won't be exclusive (as they have been for search)," he writes. "As with other app stores, Sun will charge for distribution--but unlike other app stores, whose audiences are tiny, measured in the millions or tens of millions, ours will have what we estimate to be approximately a billion users. That's clearly a lot of traffic, and will position the Java App Store as having just about the world's largest audience."

From Fierce Mobile Content

The j2me applications come with a pair of file: a jad and a jar file. The Blackberry devices require application in a particular format: .cod file. Here, we'll describe a fast procedure to obtain a cod file from your midlet.

Before proceed be sure you have installed the Blackberry JDE (downloadable from the Blackberry developer website: download here) and the Java SDK from Sun (download here).

Here you are the steps:

• Move your JAD and JAR in the bin directory of the JDE installation folder (i.e. c:\program files\Research in Motion\Blackberry JDE 4.7.0\bin\ that will make easier the process from the command line);
  
• Open a DOS shell windows, go to the bin directory mentioned before and call the RAPC command: rapc import="c:\Program Files\Research in Motion\Blackberry JDE 4.7.0\lib\net_rim_api.jar" codename=myMidelt -midlet jad=myMidlet.jad myMidlet.jar. Use the name of your application instead of the myMidelt used in the previously written command line
• Now you have your cod file, use the javaloader (after you have linked your device to the pc through usb cable) to send the application to your phone: javaloader -usb load filename.cod

One of the biggest challenge for a J2ME developer is keep the jar size of his applications as smaller as possible.

Adding new features and images to have a cooler application make the aim very difficult to achieve. There are best coding practices to reach the goal but sometimes have some software help is nice.

I have found this utility called KJar that recompress your jars giving a smaller size than with the normal jar utility. I'm using the utility after the obfuscation step for my J2ME applications. For one application I have of 290 kb, I reduced to 277 kb using KJar.

The syntax of the command to use is:

kjar [options] in.jar [out.jar]

The options are:

-s Adjust size in JAD file (if existing)
-u:url Add URL path to JAD MIDlet-Jar-URL parameter

Kjar is a windows command tool and it can be downloaded clicking here

Despite the '\n' can be used in any string in J2ME applications, with S60 Editions up till S60 3rd Edition, Feature Pack 1, the new line is not inserted properly in the Alert and the message remains in the same line (at least until it fits in the alert width).

The issue has been fixed starting from S60 3rd Edition, Feature Pack 2.

Read more at the Forum Nokia Wiki