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Groups > comp.lang.java.programmer > #17733
| From | Robert Klemme <shortcutter@googlemail.com> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: hashCode |
| Date | 2012-08-12 17:06 +0200 |
| Message-ID | <a8pv38F9ouU1@mid.individual.net> (permalink) |
| References | <563f186a-edb3-4311-ae48-3af7decfce2c@googlegroups.com> <k03d6p$2bt$1@dont-email.me> <6ac6c252-c370-4f74-b29d-ce5368019977@googlegroups.com> <502598d0$0$287$14726298@news.sunsite.dk> |
On 11.08.2012 01:27, Arne Vajhøj wrote:
> On 8/10/2012 6:22 PM, bob smith wrote:
>> On Friday, August 10, 2012 11:34:28 AM UTC-5, Eric Sosman wrote:
>>> On 8/10/2012 11:47 AM, bob smith wrote:
>>>> Is it always technically correct to override the hashCode function
>>>> like so:
>>>> @Override
>>>> public int hashCode() {
>>>> return 1;
>>>> }
>>>> Would it be potentially better if that was Object's implementation?
>>>
>>> Define "better."
>>
>> Better in the sense that you would never HAVE to override hashCode.
>>
>> Now, there are cases where you HAVE to override it, or your code is
>> very broken.
>
> It is not broken.
>
> It will perform poorly in many cases.
Well, I would go as far as to say that it will perform poorly in all
cases where hashCode() is actually needed - and that makes it broken.
The whole idea of hashing is based on the fact that the hash code
_somehow_ represents the item to be hashed. If all items have the same
constant hash code there is no point in hashing at all. So while it
does work, it does not work as intended.
Kind regards
robert
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
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hashCode bob smith <bob@coolfone.comze.com> - 2012-08-10 08:47 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-10 12:13 -0400
Re: hashCode markspace <-@.> - 2012-08-10 10:13 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-10 13:38 -0400
Re: hashCode rossum <rossum48@coldmail.com> - 2012-08-11 10:36 +0100
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-10 12:34 -0400
Re: hashCode bob smith <bob@coolfone.comze.com> - 2012-08-10 15:22 -0700
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-10 15:32 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-10 19:30 -0400
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-11 16:24 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 22:15 -0400
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 22:29 -0400
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-11 22:43 -0400
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 22:54 -0400
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-11 21:46 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-12 16:53 -0400
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-12 17:00 -0400
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-10 19:27 -0400
Re: hashCode Robert Klemme <shortcutter@googlemail.com> - 2012-08-12 17:06 +0200
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-12 16:59 -0400
Re: hashCode Robert Klemme <shortcutter@googlemail.com> - 2012-08-13 19:17 +0200
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-19 19:42 -0400
Re: hashCode Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-21 10:30 +0000
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-19 19:47 -0400
Re: hashCode Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-21 10:43 +0000
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-27 19:04 -0400
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-27 16:55 -0700
Re: hashCode markspace <-@.> - 2012-08-27 17:03 -0700
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-27 17:49 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-27 21:37 -0400
Re: hashCode Patricia Shanahan <pats@acm.org> - 2012-08-27 18:58 -0700
Re: hashCode markspace <-@.> - 2012-08-27 21:19 -0700
Re: hashCode Patricia Shanahan <pats@acm.org> - 2012-08-28 01:06 -0700
Re: hashCode markspace <-@.> - 2012-08-28 09:19 -0700
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-28 16:33 -0700
Re: hashCode markspace <-@.> - 2012-08-28 17:02 -0700
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-29 11:06 -0700
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-29 14:49 -0400
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-29 13:40 -0700
Re: hashCode Gene Wirchenko <genew@ocis.net> - 2012-08-29 18:02 -0700
Re: hashCode Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2012-08-31 00:52 +0200
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-30 21:43 -0400
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-30 21:52 -0400
Re: hashCode Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2012-08-31 04:18 +0200
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-08-31 09:08 -0600
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-31 11:38 -0400
Re: hashCode Robert Klemme <shortcutter@googlemail.com> - 2012-08-31 17:55 +0200
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-08-31 09:56 -0600
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-31 14:32 -0400
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-08-31 14:38 -0600
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-31 15:33 -0700
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-08-31 16:41 -0600
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-31 16:26 -0700
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-09-02 11:54 -0600
Re: hashCode Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2012-09-03 00:47 +0200
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-09-03 21:44 -0600
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-08-31 09:08 -0600
Re: hashCode Robert Klemme <shortcutter@googlemail.com> - 2012-08-31 17:58 +0200
Re: hashCode markspace <-@.> - 2012-08-29 11:51 -0700
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-29 13:28 -0700
Re: hashCode markspace <-@.> - 2012-08-29 16:05 -0700
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-29 16:23 -0700
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-29 20:56 -0400
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-30 11:19 +0200
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-30 10:03 -0700
Re: hashCode Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-08-30 18:34 +0000
Re: hashCode Jim Janney <jjanney@shell.xmission.com> - 2012-08-30 08:11 -0600
Re: hashCode Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-08-30 10:06 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-30 19:16 -0400
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-28 13:58 -0700
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-28 13:56 -0700
Re: hashCode Patricia Shanahan <pats@acm.org> - 2012-08-28 14:07 -0700
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-28 14:38 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-27 21:12 -0400
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-11 07:58 -0400
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-11 16:29 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 22:16 -0400
Re: hashCode Patricia Shanahan <pats@acm.org> - 2012-08-12 03:46 -0700
Re: hashCode Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-08-12 12:23 -0400
Re: hashCode Patricia Shanahan <pats@acm.org> - 2012-08-12 09:40 -0700
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-12 13:59 -0400
Re: hashCode Patricia Shanahan <pats@acm.org> - 2012-08-12 11:17 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-12 17:02 -0400
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-12 19:03 +0200
Re: hashCode Roedy Green <see_website@mindprod.com.invalid> - 2012-08-10 12:17 -0700
Re: hashCode Lew <lewbloch@gmail.com> - 2012-08-10 12:45 -0700
Re: hashCode Roedy Green <see_website@mindprod.com.invalid> - 2012-08-11 04:54 -0700
Re: hashCode Joerg Meier <joergmmeier@arcor.de> - 2012-08-11 18:25 +0200
Re: hashCode Mike Winter <usenet@michael-winter.me.invalid> - 2012-08-11 18:53 +0100
Re: hashCode Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-08-11 09:56 -0700
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-11 18:58 +0200
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 22:40 -0400
Re: hashCode rossum <rossum48@coldmail.com> - 2012-08-11 18:47 +0100
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-10 19:25 -0400
Re: hashCode Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-11 08:00 -0400
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 09:49 -0400
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-11 15:33 +0200
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-11 15:34 +0200
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-11 16:34 -0700
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-11 16:37 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-11 22:19 -0400
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-11 21:48 -0700
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-12 12:08 +0200
Re: hashCode Jan Burse <janburse@fastmail.fm> - 2012-08-12 12:18 +0200
Re: hashCode Lew <noone@lewscanon.com> - 2012-08-12 11:27 -0700
Re: hashCode Arne Vajhøj <arne@vajhoej.dk> - 2012-08-12 17:11 -0400
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