Never said Java couldn't run on other mobile OS. I said, it doesn't. Learn to read. And it isn't a matter of "knowing what you're doing", either. Java, currently, will not run on iOS, WP, or RT. There is no JVM for any of those three platforms, so how could it run? It can't, and it won't. Java is platform independent, that is true. But only, if you have a JVM installed. It is the same situation with Flash (with ActionScript), and C#. They're platform independent, if you've got a plugin installed (flash's case). The above three platforms, and most mobile OS in general, don't. Which is why I called Java, "desktop platform independent".
I think it is you who needs to go back and learn more about programming, because you clearly know nothing. So, to recap: no matter what you think you know, Java WILL NOT run without a JVM. iOS, WP, and RT DO NOT have a JVM built into the OS anywhere, so it is not a matter of systems internals. End of discussion.