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Groups > comp.lang.java.programmer > #23588

Re: <? extends String>

From Daniel Pitts <newsgroup.nospam@virtualinfinity.net>
Newsgroups comp.lang.java.programmer
Subject Re: <? extends String>
References (6 earlier) <atggb3Fsg5U1@mid.dfncis.de> <e02i4a-8m3.ln1@s.simpson148.btinternet.com> <9h4i4a-kvp.ln1@tempest.fredriksson.dy.fi> <dfgi4a-1n7.ln1@s.simpson148.btinternet.com> <IOGdnQaIDP0wN-vMnZ2dnUVZ7sSdnZ2d@bt.com>
Message-ID <a5ydt.5455$J9.2068@newsfe09.iad> (permalink)
Date 2013-04-23 08:50 -0700

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On 4/23/13 8:37 AM, lipska the kat wrote:
> On 23/04/13 14:55, Steven Simpson wrote:
>> On 23/04/13 11:31, Donkey Hottie wrote:
>>> 23.04.2013 12:48, Steven Simpson kirjoitti:
>>>> public static String generateWindowsArgument(List<? extends String>
>>>> args) {
>>> <offtopic>java.lang.String is final, so nothing can extend it.
>>> </offtopic>
>>
>> It's a matter of habit drawn from the general principle that if I don't
>> need to modify the list, I don't impose the additional, unnecessary
>> constraint on the caller, regardless of the element type.
>
> I don't understand this. In the first place List<? extends String>  says
> nothing about your ability to modify the list, you can add and remove
> Strings to your hearts content,
Wrong.

List<? extends String> listOfStuff = new ArrayList<String>();

listOfStuff.add("foo"); // compiler error here!

> secondly the only type you can pass as
> argument to generateWindowsArgument is List<String> so the construct is
> redundant anyway In fact, given that >>extends String<< is effectively
> meaningless I'm surprised the compiler doesn't at least issue a warning.
In general, it is only meaningless in that String cannot be extended in 
the current implementation of String. As Steven pointed out, that may 
not be the case for future implementations, and the compiler will never 
know that.
> I suppose you get away with it because compile time type erasure gets
> rid of any type arguments and as there can be only one type of argument
> anyway a warning would be superfluous.
Erasure is a runtime phenomenon, don't get it confused with compile-time 
static type safety.  the <? extends String> is an edge case that makes 
less sense, but if you treat it like you'd treat any other construct, 
which does no harm BTW, then you simplify your reasoning for the general 
case.

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exec problem is JDK 1.7.0_21 Roedy Green <see_website@mindprod.com.invalid> - 2013-04-16 15:48 -0700
  Re: exec problem is JDK 1.7.0_21 Lew <lewbloch@gmail.com> - 2013-04-16 16:48 -0700
  Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-20 13:00 +0300
  Re: exec problem is JDK 1.7.0_21 Joerg Meier <joergmmeier@arcor.de> - 2013-04-20 15:13 +0200
    Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-20 19:07 +0300
      Re: exec problem is JDK 1.7.0_21 markspace <markspace@nospam.nospam> - 2013-04-20 09:24 -0700
        Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-20 19:34 +0300
          Re: exec problem is JDK 1.7.0_21 markspace <markspace@nospam.nospam> - 2013-04-20 11:01 -0700
            Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 00:25 +0300
          Re: exec problem is JDK 1.7.0_21 Joerg Meier <joergmmeier@arcor.de> - 2013-04-20 22:03 +0200
            Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 00:29 +0300
              Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-20 21:56 +0000
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 08:31 +0300
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-21 11:08 +0000
                Re: exec problem is JDK 1.7.0_21 Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-04-21 13:43 -0300
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 23:12 +0300
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-21 21:17 +0000
                Re: exec problem is JDK 1.7.0_21 Arne Vajhøj <arne@vajhoej.dk> - 2013-04-27 22:49 -0400
              Re: exec problem is JDK 1.7.0_21 Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-04-20 15:03 -0700
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 08:26 +0300
                Re: exec problem is JDK 1.7.0_21 "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-04-21 14:30 +0100
                Re: exec problem is JDK 1.7.0_21 Knute Johnson <nospam@knutejohnson.com> - 2013-04-21 09:20 -0700
                Re: exec problem is JDK 1.7.0_21 markspace <markspace@nospam.nospam> - 2013-04-21 11:31 -0700
                Re: exec problem is JDK 1.7.0_21 Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-04-21 16:06 -0300
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-21 19:47 +0000
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-21 23:01 +0000
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 23:29 +0300
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 23:45 +0300
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-21 21:38 +0000
                Re: exec problem is JDK 1.7.0_21 Knute Johnson <nospam@knutejohnson.com> - 2013-04-21 18:49 -0700
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-22 09:36 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-22 10:39 +0100
                Re: exec problem is JDK 1.7.0_21 Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-04-22 07:43 -0700
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-22 19:33 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-23 07:30 +0100
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-22 21:07 +0000
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-23 23:28 +0300
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-23 21:05 +0000
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-24 11:22 +0300
                Re: exec problem is JDK 1.7.0_21 Martin Gregorie <martin@address-in-sig.invalid> - 2013-04-24 20:22 +0000
                Re: exec problem is JDK 1.7.0_21 Nigel Wade <nmw@ion.le.ac.uk> - 2013-04-24 11:24 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 23:23 +0300
            Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-21 00:40 +0300
              Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-23 10:48 +0100
                Re: exec problem is JDK 1.7.0_21 Donkey Hottie <donkey@fredriksson.dy.fi> - 2013-04-23 13:31 +0300
                <? extends String> (was: exec problem is JDK 1.7.0_21) Steven Simpson <ss@domain.invalid> - 2013-04-23 14:55 +0100
                Re: <? extends String> lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-04-23 16:37 +0100
                Re: <? extends String> Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-04-23 08:50 -0700
                Re: <? extends String> lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-04-23 17:30 +0100
                Re: <? extends String> Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-04-23 09:58 -0700
                Re: <? extends String> Donkey Hottie <donkey@fredriksson.dy.fi> - 2013-04-23 21:06 +0300
                Re: <? extends String> lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-04-23 19:33 +0100
                Re: <? extends String> Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-04-23 12:26 -0700
                Re: <? extends String> lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-04-24 09:08 +0100
                Re: <? extends String> Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-04-23 16:28 -0300
                Re: <? extends String> (was: exec problem is JDK 1.7.0_21) Lew <lewbloch@gmail.com> - 2013-04-23 14:12 -0700
                Re: <? extends String> Steven Simpson <ss@domain.invalid> - 2013-04-23 23:22 +0100
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-23 19:56 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-23 23:31 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-23 23:39 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-24 09:29 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-24 10:26 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-24 13:11 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-24 22:24 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-25 11:49 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-25 10:19 +0100
                Re: exec problem is JDK 1.7.0_21 "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-04-25 09:02 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-25 11:47 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-25 09:50 +0100
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-25 10:07 +0100
                Re: exec problem is JDK 1.7.0_21 "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-04-27 08:44 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-26 20:17 +0300
                Re: exec problem is JDK 1.7.0_21 Steven Simpson <ss@domain.invalid> - 2013-04-27 09:22 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-27 12:39 +0300
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-23 23:17 +0300
                Re: exec problem is JDK 1.7.0_21 Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-04-23 17:32 -0300
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-24 10:39 +0300
                Re: exec problem is JDK 1.7.0_21 "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-04-25 09:02 +0100
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-25 11:59 +0300
                Re: exec problem is JDK 1.7.0_21 Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-04-25 18:38 -0300
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-28 10:57 +0300
                Re: exec problem is JDK 1.7.0_21 Arne Vajhøj <arne@vajhoej.dk> - 2013-04-27 22:35 -0400
                Re: exec problem is JDK 1.7.0_21 Sven Köhler <remove-sven.koehler@gmail.com> - 2013-04-28 09:23 +0300
                Re: exec problem is JDK 1.7.0_21 Arne Vajhøj <arne@vajhoej.dk> - 2013-04-28 09:52 -0400
  Re: exec problem is JDK 1.7.0_21 Stanimir Stamenkov <s7an10@netscape.net> - 2013-04-20 17:52 +0300
    Re: exec problem is JDK 1.7.0_21 Arne Vajhøj <arne@vajhoej.dk> - 2013-04-27 22:31 -0400

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