Good advice: dont try to enter JavaME!

There are like 200 different specs you need to adapt the game to,
porting will be 80% of the dev time. And you need a dozents of
phones to make a rough check if its runs about ok.

Target Android or iOS. Dont spend time on JavaME or Symbian, Blackberry etc..

(I made several JavaME games, its a pain)