Re: A Java "interface" declaration does not allow a constructor to be specified in it ...

From: Oscar kind (oscar_at_danwa.net)
Date: 11/09/04 

Date: Tue, 9 Nov 2004 19:11:07 +0100

xarax <xarax@email.com> wrote:
>
> If Java supported full multiple inheritance (which is
> the implication of interface constructors), then there
> would be no need for interfaces; just use abstract classes
> in place of interfaces.

Which poses other problems. Imagine the following (but please bear with
the slightly off analogy):

abstract class Person has a non-abstract method "transport", that
implements walking.

abstract class MailDelivery has a non-abstract method "transport", which
implements mail delivery.

class MailMan extends both, and thus inherits the method transport from both
classes. For some reason, there is no reason to override it. Now please
think about these questions:
- Which one is inherited?
- If one is chosen automatically, what about dependencies in another
  superclass? The two methods may have an incompatible contract.
- If the method autometically becomes abstract, why? Abstract methods are
  always marked thus (either by the keyword abstract or by being defined
  in an interface).
- How do you select the transport method from Person? Extend the syntax
  again, with Person.super.transport()? It's hardly efficient to get a
  complicated, arcane syntax. 

-- 
Oscar Kind                                    http://home.hccnet.nl/okind/
Software Developer                    for contact information, see website
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