Java (J2ME) is one of the most popular game development platform across all brands of mobile devices, you can play most of the java games (.jar files) interchangeably on all mobile devices supporting Java, while java games can be played on all devices supporting Java different screen resolution becomes a problem, for example a game developed for Nokia N73 will display fine on mobile-devices having screen resolution 240 x 320 (QVGA) but will display small on a bigger screen resolution like Nokia N80 (352*416), to fix mobile game resolution optimal to your cellphone display size free utility "S60 Jar Resize" comes to the rescue, the handy little utility lets you manipulate the hardcoded screen-resolution inside the Java game file (.Jar file) for optimal display on your mobile device.
Using S60 Jar Resize is pretty simple, just select the source and destination resolution and point the application to the .Jar game file.