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Re: Instantiate an abstract class

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On 04/05/2011 05:14 PM, Rob McDonald wrote:
> Now, we all know that you can't instantiate an abstract class -- but I
> want to anyway...  Actually, I would like my abstract class to be able
> to instantiate another instance of whatever concrete class it is at
> the time.

Your class is abstract, so you can easily have:

abstract class AFoo {
   public abstract AFoo makeInstance();
}

Or, as Patricia mentions:

abstract class AFoo {
   public abstract AFoo clone(); // Legal only in Java 5+
}

Each subclass would then implement this method as appropriate.

I can answer your question more directly with reflection, but it's a 
method I wouldn't recommend without a very compelling reason why this 
approach wouldn't work for you.
-- 
Beware of bugs in the above code; I have only proved it correct, not 
tried it. -- Donald E. Knuth

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Instantiate an abstract class Rob McDonald <rob.a.mcdonald@gmail.com> - 2011-04-05 14:14 -0700
  Re: Instantiate an abstract class Patricia Shanahan <pats@acm.org> - 2011-04-05 14:37 -0700
    Re: Instantiate an abstract class Rob McDonald <rob.a.mcdonald@gmail.com> - 2011-04-05 14:49 -0700
  Re: Instantiate an abstract class Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-04-05 17:48 -0400
    Re: Instantiate an abstract class Rob McDonald <rob.a.mcdonald@gmail.com> - 2011-04-05 14:54 -0700
      Re: Instantiate an abstract class Patricia Shanahan <pats@acm.org> - 2011-04-05 15:09 -0700
      Re: Instantiate an abstract class Lew <noone@lewscanon.com> - 2011-04-06 12:43 -0400
        Re: Instantiate an abstract class "John B. Matthews" <nospam@nospam.invalid> - 2011-04-06 22:07 -0400
  Re: Instantiate an abstract class Roedy Green <see_website@mindprod.com.invalid> - 2011-04-05 19:02 -0700
  Re: Instantiate an abstract class Roedy Green <see_website@mindprod.com.invalid> - 2011-04-05 19:42 -0700
  Re: Instantiate an abstract class Lothar Kimmeringer <news200709@kimmeringer.de> - 2011-04-06 18:26 +0200
    Re: Instantiate an abstract class Lew <noone@lewscanon.com> - 2011-04-06 12:49 -0400
      Re: Instantiate an abstract class Patricia Shanahan <pats@acm.org> - 2011-04-06 10:09 -0700
      Re: Instantiate an abstract class Lothar Kimmeringer <news200709@kimmeringer.de> - 2011-04-07 01:01 +0200
  Re: Instantiate an abstract class Wojtek <nowhere@a.com> - 2011-04-06 12:41 -0700

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