Is a Class special when it has no members?

I just realize some of my classes have no members. It has several public functions and maybe private functions and everything is passes through params. I realize functional programmers do this all the time but is this class considered special if it access nothing outside of the class and only uses its params for reading (except for out params and return values)?

I know this class can be stat开发者_如何学运维ic but static classes can modify outside variables. I want to know if this is a technique or maybe if a language may give additional benefits for writing it this way and etc.

-edit- This is looking like a wiki so lets make it one.

It is just called "stateless". Nothing really special about it.

There is nothing wrong with a class that has no members; controllers do this very frequently.

Yes, you could go static, but by not being static you allow for inheritance from your memberless class, which could add members along the way, if you so desired.

If there are no members, then there is no need for a class other than having a namespace. If you were programming in Python, then you would just put those methods into a module and don't bother with a class. If you are working in Java, then a a class is a must. If you are working in C++, it's up to you - but maybe you should consider using just a namespace, instead of a class, to make it less confusing.

Yes, this makes the class completely thread safe and thus no locking is required. To me, that is a fantastic attribute.

Sane programming languages allow you to define functions outside of classes when the functions do not require any persistent data - if you can define it in an appropriate namespace, all the better. If your language does not allow that, at least define them in a static class so it's clear that no state is accessed or mutated. Overall, though, this reminds me of an excellent article on the illogical abuse of classes in the name of "pure OOP".

I'd make the class static. I don't see what advantage it would give to keep it non-static. But then again - I'm a .NET developer, not Java. The languages are close, but there are many subtle differences I'm not aware of.

Remember that all methods of your class (even stateless) have one special variable -- pointer/reference to object - this (self, whatever) for which they are applied to.

Thus it is perfect sense in such stateless class if its methods could be overridden: in this case you have to have class to provide dispatching by this. (Of course it's just emulating of first-class functions, so if your language already has ones it's no sense in this technique.)

At the moment I can't imagine why would you need stateless class without any virtual method. Unless you want to have nice auto-complete in your IDE by typing objectName and dot :)

its simple class there is no specialty in it.

But i dont understand what is the use of having public or private methods when there in no member in it. because member methods are those which acts on particular instance's state.

Yes you can have static methods in it.