Сool, NokiaUI .jar works good, though it is probably better to use some older SDK so all textures look normal. BTW, is this just a test case, or you thought about making a full Java RPG game?
I was working on a full Java game - it was going to be an FPS (S=Stabber :-P), not RPG though. The main reason i stopped was that this was before the days of iOS and Android (notice that most dates are from 2006) and J2ME fragmentation was
severe - phones not only had different OSes, but even different implementations of the Java virtual machine (each with its own bugs) with many needing phone-specific patches and tweaks even for individual models. As i wrote in the 2019 post, i basically lost interest due to that.
Nowadays Android is in a much better situation (in that you don't need a warehouse full of phones to test it in various models) though it has other issues, like pretty much all phones not having physical controls. Not that you can't make some nice games on a touch screen (e.g. turn based dungeon crawlers work fine), but personally i prefer having real buttons to press.