You can convert jar to apk !
These are the steps you have to follow :
1) Select a jar file. Two possibilities : you've got it on the internet, or on your computer. In the 2nd case, you must create the jad file (if you don't already have it), by using jadMaker
2) Go here
, and select the url of the file or choose the files to upload from your computer, and let the website do the job !!
The only thing is that it takes some time. But usually, it works !
Hope it will work for you (some jar files aren't supported, I guess) !!!