Hot swapping is very very useful, especially for creating OpenGL applications. And you can create a Java application which uses OpenGL ES 2.0 API - the same API version as WebGL.
Yes, because Java is statically typed and generally more verbose, you'll probably have to make a few more keystrokes, but if you are using Eclipse which, can auto complete most of the repetitive typing, I don't believe this to be a problem.
You also don't need to create a complicated hierarchy structure with multiple interfaces, abstract classes and so on. You can keep your application simple.
As an added bonus it will be easy for you to port your application to Android!