Groups > comp.lang.java.programmer > #4654

Re: Java generics and type erasure

From	Lew <noone@lewscanon.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: Java generics and type erasure
Date	2011-05-27 13:27 -0400
Organization	albasani.net
Message-ID	<iromsk$i6b$1@news.albasani.net> (permalink)
References	(16 earlier) <4ddf14c8$0$67785$c30e37c6@exi-reader.telstra.net> <irncmt$k84$1@news.albasani.net> <4ddf5baf$0$67779$c30e37c6@exi-reader.telstra.net> <irobpe$njg$2@news.albasani.net> <slrnitvmba.phi.avl@gamma.logic.tuwien.ac.at>

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Andreas Leitgeb wrote:
> Lew wrote:
>> OK, so I shouldn't have said "bytecode", I should've said "class file", two
>> terms that I treat interchangeably.  It's in the freaking CLASS FILE, right?
>> Isn't that the thing that gets used at runtime?  Doesn't the generic
>> information in THE CLASS FILE get ignored at runtime just like I said?

> It's not so much a question of whether the generic information of a
> class file (like java/util/ArrayList.class) is used or not, but rather
> whether the generic information of a particular *use* of that class was
> in the *using* code's class-file, which I think isn't:
>    ... = new ArrayList<ArrayList<ArrayList<Boolean>>>();

Ah, gotcha.

To eliminate my inverted way of expressing it, then, generics effectively 
don't exist at runtime because erasure occurs before runtime.  Generics errors 
occur at compilation.  Exceptions not prevented by the generics checks at 
compilation occur at runtime, just as they would have were generics never 
used, because at runtime the erasure has already occurred and the generics 
information effectively no longer exists (but for some non-relevant classfile 
information).

Thank you all for helping to clarify this.

-- 
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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Java generics and type erasure Marcin Pietraszek <m.pietraszek@gmail.com> - 2011-05-23 13:18 -0700
  Re: Java generics and type erasure "John B. Matthews" <nospam@nospam.invalid> - 2011-05-23 22:54 -0400
    Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-24 01:45 -0400
      Re: Java generics and type erasure Marcin Pietraszek <m.pietraszek@gmail.com> - 2011-05-24 12:39 -0700
      Re: Java generics and type erasure Ian Shef <invalid@avoiding.spam> - 2011-05-24 20:04 +0000
        Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-24 17:06 -0400
          Re: Java generics and type erasure Ian Shef <invalid@avoiding.spam> - 2011-05-24 23:05 +0000
            Re: Java generics and type erasure Susan Calvin <s.calvin@usr.invalid> - 2011-05-25 00:13 +0000
              Re: Java generics and type erasure Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-26 10:18 +1200
                Re: Java generics and type erasure Susan Calvin <s.calvin@usr.invalid> - 2011-05-26 01:12 +0000
                Re: Java generics and type erasure Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-26 13:59 +1200
                Re: Java generics and type erasure Susan Calvin <s.calvin@usr.invalid> - 2011-05-26 04:18 +0000
                Re: Java generics and type erasure Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-26 18:48 +1200
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-26 18:34 +1000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-26 07:45 -0400
                Re: Java generics and type erasure "John B. Matthews" <nospam@nospam.invalid> - 2011-05-26 15:25 -0400
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-27 12:01 +1000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-26 22:15 -0400
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-27 13:04 +1000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-27 01:27 -0400
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-27 18:07 +1000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-27 10:18 -0400
                Re: Java generics and type erasure Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-27 17:03 +0000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-27 13:27 -0400
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-30 15:19 +1000
                Re: Java generics and type erasure Tom McGlynn <taqmcg@gmail.com> - 2011-05-26 19:53 -0700
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-27 01:30 -0400
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-27 18:09 +1000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-27 10:22 -0400
                Re: Java generics and type erasure Esmond Pitt <esmond.pitt@bigpond.com> - 2011-05-30 15:23 +1000
                Re: Java generics and type erasure Lew <noone@lewscanon.com> - 2011-05-30 02:35 -0400

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