is it possible to make superclass extend another class ?

[krislioe]

Hi all,

I have Class A as superclass.

I have Class B extend Class A
Then Class C extend Class B

Is it possible to make Class A Extend Class D ?

Thank you,
xtanto

 

[Andrew Thompson]

I have Class A as superclass.

I have Class B extend Class A
Then Class C extend Class B

Is it possible to make Class A Extend Class D ?

Sure. So long as D extends none of A, B or C.

BTW - are you sure this is the best design?
A lot of layers of 'extends' sometimes suggests 'no'.
(and those are silly class names - even for an abstraction)

Andrew T.

 

[paul_himanshu]

Sure. So long as D extends none of A, B or C.

BTW - are you sure this is the best design?
A lot of layers of 'extends' sometimes suggests 'no'.
(and those are silly class names - even for an abstraction)

Andrew T.

 

[Patricia Shanahan]

Sure. So long as D extends none of A, B or C.

BTW - are you sure this is the best design?
A lot of layers of 'extends' sometimes suggests 'no'.
(and those are silly class names - even for an abstraction)

Andrew T.

A couple of additional restrictions:

A must be a class you can change.

A's immediate superclass must also be a superclass of D, trivially true
if A is a direct subclass of Object.

I share Andrew's doubts about a design with that many layers.

Patricia

 

[krislioe]

Hi,
Thank you for your response.

I share Andrew's doubts about a design with that many layers.

As a rule of thumb, how many is indicating too many ?

Thank you,
xtanto

 

[Patricia Shanahan]

> Hi,
> Thank you for your response.
>
>
> As a rule of thumb, how many is indicating too many ?
>

I don't think there is any rule of thumb, but an increasing queasiness
as the number of inheritance levels increases. We have at least 5 levels
here (Object, D, A, B, C). Whether it makes sense to go that deep
depends on what the classes are about, but it is deep enough that I
would question it in my own code.

Patricia