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Groups > comp.lang.java.programmer > #23590
| From | Daniel Pitts <newsgroup.nospam@virtualinfinity.net> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: <? extends String> |
| References | (8 earlier) <9h4i4a-kvp.ln1@tempest.fredriksson.dy.fi> <dfgi4a-1n7.ln1@s.simpson148.btinternet.com> <IOGdnQaIDP0wN-vMnZ2dnUVZ7sSdnZ2d@bt.com> <a5ydt.5455$J9.2068@newsfe09.iad> <j-OdnXHhU_CoKuvMnZ2dnUVZ8qednZ2d@bt.com> |
| Message-ID | <25zdt.2945$N74.2063@newsfe10.iad> (permalink) |
| Date | 2013-04-23 09:58 -0700 |
On 4/23/13 9:30 AM, lipska the kat wrote:
> On 23/04/13 16:50, Daniel Pitts wrote:
>> 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!
>
> erk, you're right, well I never, however it doesn't say anything about
> the list outside of the method, how therefor does it avoid 'impose[ing]
> the additional, unnecessary constraint on the caller' what constraint
> does it avoid ?
In *this* case none. In the General case.
List<? extends MyFoo> fooList1;
List<MyFoo> fooList2;
fooList1 can be assigned an instance of List<MyFoo>, or List<MySubFoo>.
fooList2 can *only* be be assigned an instance of List<MyFoo>, not
List<MySubFoo>. This is an unnecessary constraint on the caller.
Again, in the case of "String", there isn't a difference. but that is a
special edge case which needn't change the general behavior.
>
>>> 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.
>
> Well I reckon there's more chance of finding Elvis serving me with my
> weekly fish and chips but OK, I suppose there's a rempote possibility it
> might happen one day.
>
>>> 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,
>
> Erasure happens at compile time, generics are all about compile time
> type checking, erasure removes type arguments at compile time after type
> checking has occurred, the runtime system doesn't know anything about
> type erasure or generics
>
> http://docs.oracle.com/javase/tutorial/java/generics/erasure.html
>
> [snip]
>
> lipska
>
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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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