Programming languages like C# or Java feature static methods, despite being heavily object oriented.
I’m aware that there are many cases where static methods are used for performance or convenience reasons, but i can’t stop wondering if there exist actual coding problems which could not be solved without the use of static methods.
I think that some of the common cases which would be named here could be just “normal” methods, instead of being static, like:
- main: The purpose of the main-method is the creation of the very first running thread of the program and starting it. So this might as well just an object derived from a Thread class
- Loggers: Logger implementations often use static methods. I don’t see the point in that as i might want to exchange a logger for another on with an identical interface
- Math: Math functions really seem to be a perfect candidate for static methods at first sight, but there might be cases where you might want to exchange your math library transparently for another one (i.e. if you need more performance on the sin() function you might want to use an implementation with a faster, less precise algorithm if precision is not critical for your application)
- Singletons: Are considered bad practice by many. If only one instance is necessary you might think about actually creating only one instance.
So, what might be cases where static methods are really absolutely needed?
IMO, Static methods are needed while defining factories to create objects of different sub types of a given type where the choice of sub type is dependent on the inputs to this static factory method and is hidden from the client.
Your Logger example actually falls under this category where the actual logger is decided based on the package/class it is needed (ofcourse the other factory methods on Logger take other parameters to decide on the appropriate Logger instance to be returned).