Why is it that helper / Utility classes only contain static Methods ??

[Ravi Kiran Va]

Hi ,
please let me know why is it that

"Why is it that helper / Utility classes only contain static Methods"??

I got this query when i am working on a Factory Pattern in which there is a static method that will return the appropiate Object depending upon the data passed to it .

Please share your views

Thanks in advance .

[subodh k kumar]

Helper Class mainly have private constructor as well because of which it can not be extended and instantiated.So the only way to access the functionality/methods is to keep the methods static.This also helps Helper/Utility class to keep its functionality secure from unwanted overriding the method funtionality.

[Ravi Kiran Va]

Thanks for your reply , but i guess that is not the right answer (due to private constructor we are using static methods)

I guess that as the functionality needed is same for every user so a static method is provided , anybody correct me if i am wrong .

[David Newton]

It's because it's assumed there's no *reason* to instantiate it (but this is arguable)--if you don't *need* anything other than static methods, why make it instantiable or provide any non-static properties/methods?

On the other hand, purely static classes are more of a pain to use when testing the classes that use them, and although there are mocking libraries that can work around this, I'm not a big fan.

[Ravi Kiran Va]

Thanks David that was a nice explanation .

[pete stein]

It is my understanding that utility classes are stateless and that this is one reason for their methods to be static.

[David Newton]

(They're not always, though; they'll have synchronized pools, counters, etc.)

[Ravi Kiran Va]

pete stein wrote:It is my understanding that utility classes are stateless and that this is one reason for their methods to be static.

That was a good point , thanks Pete .