Groups > comp.lang.java.programmer > #11709

Re: Converting Sets

From	Roedy Green <see_website@mindprod.com.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: Converting Sets
Date	2012-02-02 05:32 -0800
Organization	Canadian Mind Products
Message-ID	<vq3li79bbkel9maksor8n63m6jr5pgsq5q@4ax.com> (permalink)
References	<11fki7dcr12je80bqi6q7ml6f0tc78965a@4ax.com> <4f2a767d$0$449$426a34cc@news.free.fr>

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On Thu, 02 Feb 2012 12:47:58 +0100, Mayeul <mayeul.marguet@free.fr>
wrote, quoted or indirectly quoted someone who said :

>Conversion of a Set<X> to a Set<? extends Y>, ensuring the Set contains 
>objects assignable to Y, but no new elements can be added to it:
>
>Set<X> setOfX = obtainSetOfX();
>Set<? extends Y> setOfY = setOfX;

This what I was looking for , that did not require an element by
element copy.
Ah, but this this you created is NOT a Set<Y>.  You cannot add
arbirary Y to it, just more X. I feel queasy. How could the compiler
keep track that setOfY could only contain X.
-- 
Roedy Green Canadian Mind Products
http://mindprod.com
One of the most useful comments you can put in a program is 
"If you change this, remember to change ?XXX? too".

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Thread

Converting Sets Roedy Green <see_website@mindprod.com.invalid> - 2012-02-01 23:34 -0800
  Re: Converting Sets Mayeul <mayeul.marguet@free.fr> - 2012-02-02 12:47 +0100
    Re: Converting Sets Roedy Green <see_website@mindprod.com.invalid> - 2012-02-02 05:32 -0800
      Re: Converting Sets Mayeul <mayeul.marguet@free.fr> - 2012-02-02 16:06 +0100
        Re: Converting Sets markspace <-@.> - 2012-02-02 09:21 -0800
          Re: Converting Sets Jim Janney <jjanney@shell.xmission.com> - 2012-02-02 13:13 -0700
            Re: Converting Sets markspace <-@.> - 2012-02-02 13:46 -0800
          Re: Converting Sets Roedy Green <see_website@mindprod.com.invalid> - 2012-02-02 16:29 -0800
            Re: Converting Sets Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-02-02 17:34 -0800
              Re: Converting Sets Arne Vajhøj <arne@vajhoej.dk> - 2012-02-04 20:49 -0500
                Re: Converting Sets Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-02-06 12:55 -0800
                Re: Converting Sets Arne Vajhøj <arne@vajhoej.dk> - 2012-02-06 20:47 -0500
                Re: Converting Sets Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-02-06 17:51 -0800
                Re: Converting Sets Arne Vajhøj <arne@vajhoej.dk> - 2012-02-06 20:57 -0500
            Re: Converting Sets markspace <-@.> - 2012-02-03 14:12 -0800
              Re: Converting Sets Lew <lewbloch@gmail.com> - 2012-02-03 22:32 -0800
            Re: Converting Sets Lew <lewbloch@gmail.com> - 2012-02-03 22:30 -0800
          Re: Converting Sets Lew <lewbloch@gmail.com> - 2012-02-03 22:33 -0800
      Re: Converting Sets Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-02-02 11:02 -0800
    Re: Converting Sets Roedy Green <see_website@mindprod.com.invalid> - 2012-02-02 18:25 -0800
      Re: Converting Sets markspace <-@.> - 2012-02-03 14:25 -0800

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