Is there a rule of thumb for when to code a static method vs an instance method?

Question

I\'m learning Java (and OOP) and although it might irrelevant for where I\'m at right now, I was wondering if SO could share some common pitfalls or good design practices.

Answer 1

My rule of thumb is: if the method performs anything related to a specific instance of a class, regardless of whether it needs to use class instance variables. If you can consider a situation where you might need to use a certain method without necessarily referring to an instance of the class, then the method should definitely be static (class). If this method also happens to need to make use of instance variables in certain cases, then it is probably best to create a separate instance method that calls the static method and passes the instance variables. Performance-wise I believe there is negligible difference (at least in .NET, though I would imagine it would be very similar for Java).