The java games for a particular mobile have fixed resolution
But if you want to change the resolution for the different mobile application you can use the software provided here to change the resolution
This simple "hack", allows running java

game developed and optimized for low resolution phones (176*208) like N70 on the high resolution phones (352*416) like N80 or phones with QVGA screens like N93 in full screen mode and its native resolution. Now a have a free PC software that allows editing and changing the screen resolution of Java applications/games to any of the stand.

Download

[V-LINKED]