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 static methods are always one of the following:

1. Private "helper" methods that evaluate a formula useful only to that class.
2. Factory methods (Foo.getInstance() etc.)
3. In a "utility" class that is final, has a private constructor and contains nothing other than public static methods (e.g. com.google.common.collect.Maps)

I will not make a method static just because it does not refer to any instance variables.