Do you believe in class inheritance? You know, this isn’t religion, its programming. I don’t believe in dogmatic coding. I believe in class inheritance for Java, because the compiler and IDE will help you.
That being said, will I run away from Backbone’s .extend function like it’s the plague? No. Most of my Backbone classes don’t inherit, but if I have two similar models, I might base them off of a base model. I don’t create the kinds of hierarchies Java requires, and actually makes good use of. But again, once in a while, I’ll make a base class and maybe two different flavors of it, if it makes sense.