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Re: Why can't I downcast in the following code

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From	Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: Why can't I downcast in the following code
Date	Sun, 23 Oct 2011 23:16:39 -0400
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On 10/23/2011 9:22 PM, Chad wrote:
> Given the following...
>
> class X {}

     class Automobile {}

> class Y extends X {}

     class Toyota extends Automobile {}

> class Z extends X {}

     class Saab extends Automobile {}

> public class Main {
>
>      public static void main(String[] args) {
>          X x = new X();

     Automobile x = new Automobile();

>          Y y = new Y();

     Toyota y = new Toyota();

>          Z z = new Z();

     Saab z = new Saab();
>
>          Y o6 = (Y) x; //<--error

     Toyota o6 = (Toyota) x;

>      }
>
> }
>
> I get this error...
>
> run:
> Exception in thread "main" java.lang.ClassCastException: X cannot be
> cast to Y

     Exception ... Automobile cannot be cast to Toyota

> I thought I could cast X to Y since they inherited. Why doesn't it
> work in this case?

     Because all Toyotas are Automobiles, but not all Automobiles
are Toyotas.

-- 
Eric Sosman
esosman@ieee-dot-org.invalid

Thread

Why can't I downcast in the following code Chad <cdalten@gmail.com> - 2011-10-23 18:22 -0700
  Re: Why can't I downcast in the following code Chad <cdalten@gmail.com> - 2011-10-23 18:47 -0700
    Re: Why can't I downcast in the following code Travers Naran <tnaran@gmail.com> - 2011-10-24 07:57 -0700
  Re: Why can't I downcast in the following code Roedy Green <see_website@mindprod.com.invalid> - 2011-10-23 18:50 -0700
    Re: Why can't I downcast in the following code Chad <cdalten@gmail.com> - 2011-10-23 18:57 -0700
    Re: Why can't I downcast in the following code Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-10-23 19:00 -0700
      Re: Why can't I downcast in the following code Lew <lewbloch@gmail.com> - 2011-10-23 23:22 -0700
        Re: Why can't I downcast in the following code Lew <lewbloch@gmail.com> - 2011-10-23 23:27 -0700
  Re: Why can't I downcast in the following code Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-10-23 19:03 -0700
  Re: Why can't I downcast in the following code Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-23 23:16 -0400
    Re: Why can't I downcast in the following code Donkey Hottie <donkey@fredriksson.dy.fi> - 2011-10-24 07:19 +0300
      Re: Why can't I downcast in the following code Arne Vajhøj <arne@vajhoej.dk> - 2011-11-06 16:03 -0500
  Re: Why can't I downcast in the following code Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-10-24 00:08 -0500
  Re: Why can't I downcast in the following code Lew <lewbloch@gmail.com> - 2011-10-23 23:17 -0700
    Re: Why can't I downcast in the following code Lew <lewbloch@gmail.com> - 2011-10-23 23:19 -0700

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