Jar and Jad files
The java applications that you can send to your phone are either .jad or .jar,
jad is prefered, but if you don't have a file of this type you can use
JADMaker to convert a jar.
Before you can install the new software you will need to ensure that the Java
Applet Loader on your phone is enabled, excellent instructions for this can be
found
in this thread at Howardforums.