I've been coding in Java for over a dozen years now and I can say without equivocation you're either a liar who's never actually worked with it or you're a fucking troll. Write once, run anywhere is is 100% real and is so common that it's a joke. Many places I've worked at the developer develop on Windows but the code runs on a linux server. At my current place of employment, we code on Macs and deploy on Linux. We never, ever get platform issues. It's rock-fucking-solid. Now, I'm not going to say that it's impossible to have a problem but you have to be a huge moron of a programmer to run into it. For example, building filesystem paths where the path separator is hard-coded. So if you're having a problem, it's you. Learn how to write code.