We had an short argument with a collegue at work recently whether the private «stateless» methods of a class (those that do not use instance fields) should be declared static or not. My opinion was they should be static because this marks them as stateless and not only eases code reviews, but provides a compile time safety against using instance fields. This used to help me when I was digging in numerous piles of somebody else’s code. In turn his argument was that

… if someone decides that they need some state in the method it is possible that they’ll make the mistake of creating or changing a static variable instead of creating an instance variable or removing static from the method signature. Also, static methods tend to create yet more static methods, like cancer.

I don’t like declaring all methods as instance methods just because there are people with procedural language background that can’t or don’t want to fight their habits. If the field should be an instance field, don’t make it static, it just won’t work in most cases!

I am eager to hear your opinions on the case.