Re: [xmlvm-users] Interface vs abstract classes

[Leo I. <leo...@gm...>]

Java doesn't support multiple inheritance the way C++ does. This means that
If you want your class to extend multiple types, you have to use interfaces.


On Sat, Sep 11, 2010 at 8:17 AM, Panayotis Katsaloulis <
pan...@pa...> wrote:

> For quite some time there is no decision whether it is preferable to
> use abstract classes or interfaces.
> With this email I'd propose to use only abstract classes instead of
> interfaces and I hope I will convince you :)
>
> First of all I know the disadvantages. By using interfaces we can not
> reuse the same objects and thus we usually create inner classes (so we
> create one class more).
> A second problem has to do with concept: in ObjC there is a use of
> protocols and not interfaces.
>
> The problem is, although it looks like we make economy by reusing the
> same object, in reality under the current xmlvm implementation, this
> is not the case. In order to properly support java interfaces, a
> "secret" glue object is used in every case (in which object we have
> absolutely no control upon).
>
> When using abstract classes there is 1-1 correspondence. Even if we
> use inner classes (which is a common and well known technique), we
> have absolute control on this object. In any case, worst case
> scenario, we have to define/use one (an only one) object of this
> abstract class.
>
> Back to the interface implementation, the minimum number of objects is
> one: the glue object. Though, in the case of an inner object (or any
> time we don't reuse a given object) , the number of objects rises to
> two!
>
> In all cases, interface implementation is more demanding than abstract
> classes, and more complex. For this reason I propose to use everywhere
> in XMLVM compatibility library abstract classes instead of interfaces
> - even for trivial cases.
>
> --
> Panayotis
>
>
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