Multiple casting on inherited objects

Question

interface I{
}
class A implements I{
}

class B extends A {
}

class C extends B{

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

        b = (B)(I)a; //Line 1
    }
}

I know this is not an actual code :)

I just need to know how the casting gets done at Line 1.

I know the reference variable 'a' gets cast to Class B/Interface I.

But I am not sure of the sequence in which the casting takes place..can someone tell me which cast gets executed first.

PS : I searched for similar posts but most of them were from C++.If a similar post is already there wrt to Java do point it..tx

You can't cast a cast to a cast: a -> I -> B.

Jeroen Vannevel
– Jeroen Vannevel

2013-08-25 15:42:44 +00:00
Commented Aug 25, 2013 at 15:42 — Jeroen Vannevel
– Jeroen Vannevel, Commented Aug 25, 2013 at 15:42

qaphla · Accepted Answer · 2013-08-25 15:41:49Z

3

a gets cast to type I first, and then to type B, as casting is right-associative.

answered Aug 25, 2013 at 15:41

qaphla

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Comments

Luka · Accepted Answer · 2013-08-25 16:10:19Z

0

Why would you cast it in the first place? This is multiple level inheritance but what happens here is all them methods in class I get inherited by class A, as class B inherits class A the methods in class A get passed onto class B. This means that all the methods class A inherits will also be in class B

That means class B is also a type of class I and therefore i believe there is no need to cast at all

answered Aug 25, 2013 at 16:10

Luka

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