Write once, run everywhere?

Wasn't one of the main goals of Java the ability to write once, run everywhere? Good luck trying to run different Java applications on the same machine.  I can't imagine a worse technology when it comes to maintaining backwards compatibility, which forces users to maintain multiple versions of Java.

Could Blue Stacks be the solution?

From the Technology Review Article about BlueStacks:

A startup called BlueStacks wants to end all your worrying about whether an app will run on a specific operating system. The company's technology, which it's showing off at trade shows, lets users run apps on operating systems they weren't designed for.
The  software lets Android apps run on Windows, and lets Android apps run within the browser on Google's ChromeOS. It can run Windows on top of Android or vice versa. The company will make the software available for download, but it can also be built into apps, and will come preinstalled on some hardware. "We don't care about the operating system anymore," says BlueStacks CEO Rosen Sharma. "It's all about apps."