- The Java Virtual Machine (JVM). Advantages: Great tools, hosts many languages, lots of free software is available for it (databases, support for many file formats, etc.), supports modularity (OSGi, Jigsaw).
- The web browser. Advantages: One can quickly try out an application without downloading anything, URLs encode application states and are bookmarkable, the ability to clone application states via tabs, integrates hypermedia and data streams of all kinds.
It would be modular, every aspect of it would be extensible in Java. It would be host to a new kind of web/desktop application hybrid. If the JWebPane technique of porting Webkit to Java2D really works, then it can even provide a perfect web experience (Fig 1, 2). Alas, it has been a long while since there was any news about JWebPane.
I do realize that applets go a long way in the direction of this vision, but several minor details add up so that one still feels the barrier between Java and the browser. I could never get excited about JavaFX, it always felt like Java was trying to be like Flash. But the idea of a JVM-based web browser, HotJava 2 if you will, does excite me in ways I cannot all explain rationally. I can see myself extending such a browser with many tools and writing all my future applications based on it.
Update 2010-03-02: See my comment below on a refinement of these ideas.
Update 2010-12-15: Oracle has granted my wish and turned JavaFX from a language into a library.