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>Why not make K and L as private (hidden) when they are not used anywhere else?

As I said, there is no clear indication that A, K and L are related. K and L are not really a function that the class needs to preform, thay are a funcion that A needs to call out to.

> Users will not see them in interface in such case when using class somewhere.

It isn't the user that this is for, it is the developer/maintainer of the class that has to look at all 12 methods.