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generics

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I have been reading through the java tutorial on generics, and have a 
question relating to them.

Firstly as from the java tutorial, if I had the following 'Cage' class



	interface Animal { ... }

	interface Lion extends Animal { ... }

	interface cat extends Animal { ... }

	public Cage<E> extends Collection<E> { ... }
	
	Cage<Animal> animalCage=new Cage<animal>

	Cage<Lion> lionCage=new Cage<lion>

	Cage<cat> catCage=new Cage<cat>


with the above definitions Cage is a subclass of Collection, but with 
generics as i understand it the various cages ie Cage<animal> Cage<lion> 
and Cage<cat> are not interchangable as below


	lionCage.add(catCage)// not allowed!!! even though lionCage and 
castCage are subclasses of Collection


could this be because that the various Cages take differant parameters?

thanks in advance

Neil Morris

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generics Neil Morris <neil.morris4@googlemail.com> - 2011-06-13 22:05 +0100
  Re: generics markspace <-@.> - 2011-06-13 17:49 -0700
  Re: generics Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-06-14 01:48 -0400
  Re: generics Ian Shef <invalid@avoiding.spam> - 2011-06-14 19:45 +0000
  Re: generics Neil Morris <neil.morris4@googlemail.com> - 2011-06-14 21:31 +0100
    Re: generics markspace <-@.> - 2011-06-14 14:21 -0700
      Re: generics Lewis Bloch <lewisbloch@google.com> - 2011-06-16 07:05 -0700
        Re: generics Patricia Shanahan <pats@acm.org> - 2011-06-16 11:40 -0700
        Re: generics Gene Wirchenko <genew@ocis.net> - 2011-06-16 15:14 -0700

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