Contructor "good or bad"

[Vxyz eom]

Hello Folks !
I have a problem and doubts with constructors.
does any one tell me why constructor with parameters cannot be inherit ???remember the fact that default constructor can inherit.

class A
{
 void A()
{
 System.out.println("Hello ! I am A");
}
}
class B extends A
{
 
 public static void main(String args[])
{
 A a=new A();
}
}

this works well.
But

class A
{
 void A(int b)
{
 System.out.println("Hello ! I am A"+i);
}
}
class B extends A
{
 
 public static void main(String args[])
{
 A a=new A(5);
}
}

Not Working Explain with Details ....!!!

[vibhor sharma]

I doubt even first one works well ..

 void A()
{
 printf("Hello ! I am A");
}

It is not a constructor , eventually a valid java method which happens to be a same name as a class name .... remember constructors doesn't have return type, not even void .

PS : In my opinion constructors cant be inherited , be it default one ...

[Matthew Brown]

Here's what's going on...

You aren't specifying a constructor for the B class. So the compiler inserts a default constructor, taking no arguments.

Because B is a subclass of A, any constructor of B must call a constructor of A. Again, if you omit this, the compiler will insert the call for you. But it can only insert a no-arg constructor like this. In the second case, there isn't a no-arg constructor. So if you want to inherit from B in that case you need to put in the constructor calls explicitly. For instance, like this:

class A {
    A(int b) {
        printf("Hello ! I am A"+i);
    }
}
class B extends A {
    B(int b) {
        super(b);
    }

    public static void main(String args[]) {
        A a=new A(5);
    }
}

Actually, writing that I've realised there were two problems. Your examples didn't have any constructors. They were ordinary methods - constructors don't have a return type.

[Vxyz eom]

vibhor sharma wrote:I doubt even first one works well ..

 void A()
{
 printf("Hello ! I am A");
}

It is not a constructor , eventually a valid java method which happens to be a same name as a class name .... remember constructors doesn't have return type, not even void .

PS : In my opinion constructors cant be inherited , be it default one ...

Now is it correct Vibhor ???

[Vxyz eom]

Matthew Brown wrote:Here's what's going on...

You aren't specifying a constructor for the B class. So the compiler inserts a default constructor, taking no arguments.

Because B is a subclass of A, any constructor of B must call a constructor of A. Again, if you omit this, the compiler will insert the call for you. But it can only insert a no-arg constructor like this. In the second case, there isn't a no-arg constructor. So if you want to inherit from B in that case you need to put in the constructor calls explicitly. For instance, like this:

class A {
    A(int b) {
        printf("Hello ! I am A"+i);
    }
}
class B extends A {
    B(int b) {
        super(b);
    }

    public static void main(String args[]) {
        A a=new A(5);
    }
}

Actually, writing that I've realised there were two problems. Your examples didn't have any constructors. They were ordinary methods - constructors don't have a return type.

Thanks Matthew You are Correct.