Some Nokia, Samsung phone models need both .jar and .jad file when installed java games and apps, *.jad is the file that contains information about the game,*.Jar is the application/game file. here are the two JAD generators. 

1, Jadmaker: http://www.geocities.com/mangokun/jadmaker/jadmaker.htm

                jadmaker download link: JADMaker.zip

2, JadGen:

To make .jad files for the .jar you have downloaded onto your pc.
Just drag the .jar on top of the jadgen.exe , this will create a .jad file