What is the benefit of defining a class like this?

Question

I have just seen this code and I cannot see what is the benefit of defining a class in this way. Can anyone explain me why/when we use this notation?

At first I thought that an instance of ClassW would allow you to access methods from ClassB and ClassC but I see it doesn't. It is just a notation... but why?

class ClassW extends ClassZ {
}

abstract class ClassZ extends ClassA<ClassB, ClassC> {
}

class ClassA<B extends ClassB, C extends ClassC> {
    B b;
    C c;
}

abstract class ClassB {     
    public abstract void isB();     
}

abstract class ClassC {     
    public abstract void isC();     
}

http://docs.oracle.com/javase/tutorial/java/generics/bounded.html — JB Nizet, Oct 04 '14 at 09:36
Hi JB Nizet. Thank you for your reply, it answers what I was asking. — daniel sp, Oct 06 '14 at 08:37

score 0 · Accepted Answer · edited May 23 '17 at 10:28

0

It means that B can be ClassB or any subtype of ClassB, and C can be ClassC or any subtype of ClassC. So you are specifying that is what you allow as the types B and C.

You can find some additonal good answers here

edited May 23 '17 at 10:28

Community

1
1

answered Sep 29 '14 at 09:53

pln

1,108
9
13

I don't think is that simple... for ClassA we have two definitions... ClassA. is what you say, that B can be of any class extending ClassB. – daniel sp Sep 29 '14 at 09:59
Clarify your question then, are you in fact asking what generics is ? – pln Sep 29 '14 at 10:01
I am just asking this case where you define ClassA. – daniel sp Sep 29 '14 at 10:02

What is the benefit of defining a class like this?

1 Answers1