"Breaking the API" is what we call "refactoring" in the (extremely common) case where your code is only used in a single project, and not part of a reusable lib

"Breaking the API" is what we call "refactoring" in the (extremely common) case where your code is only used in a single project, and not part of a reusable library. And yeah, if you radically rework how you make your boxes work, that's a good time to do a refactor. But there's no reason to anticipatorily add in a bunch of complexity so that you don't have to convert a value to a property at some hypothetical future point. (I mean, among other things, if you put your area property behind get/set methods, you still have to go and change all the setters anyway, since in your brave new width 'n' height world, setting area is nonsensical. So your API still breaks, and you still need to change your consuming code. What was the benefit of the getters/setters then?)