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Re: Java generics and type erasure

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On May 26, 10:01 pm, Esmond Pitt <esmond.p...@bigpond.com> wrote:
> On 26/05/2011 9:45 PM, Lew wrote:
>
>
>
> > On 05/26/2011 04:34 AM, Esmond Pitt wrote:
> >> On 26/05/2011 4:48 PM, Lawrence D'Oliveiro wrote:
> >>>> No -- presumably, it would have caused problems compiling 1.4 source
> >>>> code
> >>>> against 1.5's libraries, not running existing 1.4 bytecode linked to
> >>>> 1.5
> >>>> libraries.
>
> >>> In Java terms, what’s the difference?
>
> >> The difference is that generic type-signatures are present in .class
> >> files for
> >> compilation purposes even though generics are erased to their lower
> >> bounds at
> >> runtime, so that the compiler can enforce the semantics of generics.
>
> > This contradicts the statement that Ian Shef made upthread that type
> > erasure occurs in compilation. It seems I was correct after all, and
> > that it really does happen at runtime.
>
> No, it doesn't contradict that statement at all. Read what I wrote
> properly. Types are erased at compile time. They don't appear in the
> bytecode. Look for yourself. They do appear in method signatures, for
> the compiler. I said all that rather carefully.

Perhaps the confusion here may be due to an ambiguity in the phrase
   'generics are erased to ... at runtime'
which I could interpret in two ways.  It can mean the something is
actively erasing them at runtime, or it can mean that they have the
static characteristic of having been erased to xxx at runtime.  The
first would suggest that type erasure is happening at runtime while
the later implies that erasure has already happened, i.e., at compile
time.  While I gather you intended the later, I think someone
inferring the former has a reasonable case too.

    Regards,
    Tom McGlynn

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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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