Android : Easiest Cell Phone OS to port a Java Swing/Graphics Application to

I am developing a game using Java Swing and Java 2D graphics. I would like to port it to a Cell Phone OS. Which would be the easiest, given what I have developed it with? IOS, Android, or Windows? Or am I better off switching to one of these nuetral cell phone OS platform development kits? I'm looking for the easiest way.

Thanks.