Groups > comp.lang.java.programmer > #9145

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

From	Travers Naran <tnaran@gmail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Why can't I downcast in the following code
Date	2011-10-24 07:57 -0700
Organization	A noiseless patient Spider
Message-ID	<j83udp$opg$1@dont-email.me> (permalink)
References	<2196c265-94c4-4fcb-beb5-ddf3a7135da8@l10g2000pra.googlegroups.com> <7b2d0001-bb27-4ea2-aba3-a23b5fca59af@h23g2000pra.googlegroups.com>

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On 23/10/2011 6:47 PM, Chad wrote:
>> I thought I could cast X to Y since they inherited. Why doesn't it
>> work in this case?
>>
>
> I thought I could cast X to Y since *they are* inherited. Why doesn't
> it work in this case?

The simple answer, Chad, is that x (the variable) is NOT Y (the class). 
  You can cast a variable to the actual class it is on up.  You cannot 
turn a parent class into it's child class via casting.

Left as an exercise for the student why this is so.

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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 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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