Re: Forcing sub-classes to implement Constructor

Alright, the forcing function is more complex and probably not useful to
you...  this is what it looks like to me

(1) All classes must have a constructor.  If none is dfined, a default
one is inferred.
(2) A super class's constructor must call a sub class's constructor.  If
it is not explciit, then again the defaiult constructor is inferred

SO the forcing mechanism is that IF the super class does not have a
default constructor THEN the consructor of a sub class must expolicitly
invoke the constructor the super-class *does* have.

If the super class has no default constructor but another one.  And the
sub class has no constructor (which ends  up meaning a default
consrtuctor that attempt
to call the super's default constructor)  THEN its an error.




Brian Maso wrote:
> No.
>
> Constructors are more like static methods than regular methods: they
> can't be declared abstract and thus force subclasses to have them. You
> can add tools to your build to recognize certain annotations that
> trigger verifier rules. For example, you could define an annotation
> such as:
>
> @SubclassConstructorRequiredPattern(presense=REQUIRED,
> constructor=PUBLIC_DEFAULT)
>
> which would be applied to the base class. Some part of your build then
> would scan code either jsut before or just after compilation to see if
> it breaks all the rules defined by such annotations.
>
> Sounds like an awful lot of work, though. What's your use-case? Why do
> you ned subclasses to supply a public default constructor?
>
> Brian Maso
>
> At 07:13 AM 8/9/2007, you wrote:
>> Is there a way to force subclasses of a class to implement a certain
>> (read
>> empty) constructor.
>>
>> mvh roger j
>>
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