How to deal with the most common classes missing on J2ME

Question

I\'m trying to code an application which runs un different java platforms like J2SE, J2ME, Android, etc. I already know that I\'ll have to rewrite most of the UI for each pl

Answer 1

We faced exactly this situation in developing zxing. If J2ME is in your list of targets, this is your limiting factor by far. We targeted MIDP 2.0 / CLDC 1.1. If you have a similar requirement, you need to stick to Java 1.2. Java 1.4 language features are definitely not present (like assert) and in general you won't find anything after 1.2 in J2ME.

We did not use external libraries, but, you could package them into your deployed .jar file with little trouble. It would make the resulting .jar bigger, and that could be an issue. (Then you can try optimizers/shrinkers like ProGuard to mitigate that.)

I did end up reimplementing something like Collections.sort() and Comparator since we needed them and they are not in J2ME. So yeah you might consider doing this in cases, though only where necessary.

We used Vector and Hashtable and arrays since there is no other choice, really, in J2ME. I would just use them unless you have a reason not to, and that would be performance I guess. In theory JVM makers are already optimizing their implementation but that doesn't mean you couldn't make a better one... I guess I would be surprised if it is worth it in the vast majority of cases. Just make sure you really need to do this before putting in the effort.