Why subclass doesn't inherit constructor's superclass ?

[Julien Va]

Hi everyone,

I know that a subclass can't inherit from the constructor's superclass.
If the superclass A has 5 overloaded constructors (with different parameters), then sub-class B extending A will not have these constructors available from the outside.
if I can do: new A(param1, param2),
I cannot do: new B(param1, param2)
unless I explicitely redefine the constructors of A, in the B class (which is boring isn't it?).

And I know that I can use the super type to access at the attributes of the superclass

So, my question is : "Why the conceptors of Java prevented the constructors to be inherited?"
I need those information to make a presentation in front of my classroom.

Thank you very much for your help.

[Abimaran Kugathasan]

Julien Va wrote:
unless I explicitely redefine the constructors of A, in the B class (which is boring isn't it?).

You can't do this! Where do you get this?

Julien Va wrote:
And I know that I can use the super type to access at the attributes of the superclass

Not the super type, but, super keyword!

Julien Va wrote:
So, my question is : "Why the conceptors of Java prevented the constructors to be inherited?"

What is the logic, if you allow to construct an object of another class in you class?

[Seetharaman Venkatasamy]

In java, only members can be inherited. Constructors are not a member of a class.

[Joanne Neal]

Abimaran Kugathasan wrote:

Julien Va wrote:
unless I explicitely redefine the constructors of A, in the B class (which is boring isn't it?).

You can't do this! Where do you get this?

I think what Julien meant was that he could define 5 overloaded constructors in B which matched the signatures of the 5 constructors in A
i.e.

class A
{
    A(){}
    A(int i) {}
    A(String s) {}
    A(int i, int j) {}
    A(String s, int i) {}
}
class B extends A
{
    B(){}
    B(int i) {}
    B(String s) {}
    B(int i, int j) {}
    B(String s, int i) {}
}

[Seetharaman Venkatasamy]

Joanne Neal wrote:
I think what Julien meant was that he could define 5 overloaded constructors in B which matched the signatures of the 5 constructors in A
i.e.

class A
{
    A(){}
    A(int i) {}
    A(String s) {}
    A(int i, int j) {}
    A(String s, int i) {}
}
class B extends A
{
    B(){}
    B(int i) {}
    B(String s) {}
    B(int i, int j) {}
    B(String s, int i) {}
}

In some case[probably most of the case ], this will cause more trouble than it worth . this might be one of the reason to not allowing the inherited constructor in subclass.

[Seetharaman Venkatasamy]

Welcome to JavaRanch Julien

[Julien Va]

Seetharaman Venkatasamy wrote:Welcome to JavaRanch Julien

Thanks

But you say also :

Seetharaman Venkatasamy wrote:this will cause more trouble than it worth

Why ? Witch trouble ?

[Seetharaman Venkatasamy]

Julien Va wrote:
But you say also :

Seetharaman Venkatasamy wrote:this will cause more trouble than it worth

Why ? Witch trouble ?

For an example: suppose you dont want B to be subclass or you want to expose only default constructor to a class/subclass to avoid the confusion of many overloaded constructor.

[Julien Va]

Seetharaman Venkatasamy wrote:
For an example: suppose you dont want B to be subclass

Do you have an exemple please ?

Seetharaman Venkatasamy wrote:or you want to expose only default constructor to a class/subclass to avoid the confusion of many overloaded constructor.

I think that could be one answer. I understant what you meen. I don't think about that way until now... tanks !

[Julien Va]

Up

So, Seetharaman said that it's a solution to avoid the confusion of many overloaded constructor. I agree with him. But, do you have other proposition ?

Thank you