Java and the "chairness"

OK, I finally decided to start with Java. I want to create some applications for android and first of all I need to start with the basics.
That's what I've learnt: a class is the idea of something. If I create a chair class I don't refer to a specific chair, but to its chairness.
Sounds pretty dumb but perfectly logical.
Moreover this is really similar to Plato's philosophy, and that's just great!