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Groups > comp.lang.java.programmer > #4161
| Date | 2011-05-16 07:16 -0700 |
|---|---|
| From | Patricia Shanahan <pats@acm.org> |
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Did the sort do anything? |
| References | (4 earlier) <iqq2b2$jhm$4@lust.ihug.co.nz> <N6-dnSCv9viQDE3QnZ2dnUVZ_v6dnZ2d@earthlink.com> <iqqec4$qi7$2@lust.ihug.co.nz> <kemdnZVnBva8n0zQnZ2dnUVZ_uqdnZ2d@earthlink.com> <iqr3nv$6t5$2@lust.ihug.co.nz> |
| Message-ID | <noidndppmuNYrEzQnZ2dnUVZ_gednZ2d@earthlink.com> (permalink) |
On 5/16/2011 5:02 AM, Lawrence D'Oliveiro wrote:
> In message<kemdnZVnBva8n0zQnZ2dnUVZ_uqdnZ2d@earthlink.com>, Patricia
> Shanahan wrote:
>
>> Distinct objects probably have different identity hash codes regardless of
>> whether their fields all have the same values.
>
> “By contract, any two objects for which equals(Object) returns true must
> return the same hash code value.”
System.identityHashCode(x) does not necessarily return the same as
x.hashCode(), and usually will not unless x inherits equals and hashCode
from Object. The contracts for System.identityHashCode(x) and
x.hashCode() match if, and only if, x.equals(y) is equivalent to x==y.
> <http://developer.android.com/reference/java/lang/Object.html#hashCode%28%29>
>
> “Distinct” would presumably mean “not equal”.
It means "not the same object".
For example, equality for Integer is based only on the numeric value of
the integer the object represents. Integer objects are Comparable, with
sort order the same as numeric order of the represented integer.
Integer should be the poster child for not caring about sort stability.
This program:
public class IdentityHashCode {
public static void main(String[] args) {
Integer x = new Integer(3);
Integer y = new Integer(3);
System.out.printf("x.equals(y)=%b, x.compareTo(y)=%d, "
+ "x.hashCode()=%d "
+ "System.identityHashCode(x)=%d%n", x.equals(y), x
.compareTo(y), x.hashCode(), System.identityHashCode(x));
System.out.printf("y.equals(x)=%b, y.compareTo(x)=%d, "
+ "y.hashCode()=%d "
+ "System.identityHashCode(y)=%d%n", y.equals(x), y
.compareTo(x), y.hashCode(), System.identityHashCode(y));
}
}
produces as typical output:
x.equals(y)=true, x.compareTo(y)=0, x.hashCode()=3
System.identityHashCode(x)=4072869
y.equals(x)=true, y.compareTo(x)=0, y.hashCode()=3
System.identityHashCode(y)=11077203
Whether the sort algorithm is stable or not can affect subsequent
program behavior even for sorting Integer objects by their natural order.
Patricia
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Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-05-10 08:06 -0700
Re: Did the sort do anything? markspace <-@.> - 2011-05-10 08:48 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-14 15:33 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-14 08:56 -0400
Re: Did the sort do anything? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-14 13:54 +0000
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-15 11:16 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-14 23:24 -0400
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-15 11:20 +0100
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-15 07:00 -0400
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-15 15:09 +0100
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-16 14:28 +1200
Re: Did the sort do anything? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-05-15 22:38 -0400
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-16 19:11 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-16 03:47 -0400
Re: Did the sort do anything? markspace <-@.> - 2011-05-16 14:14 -0700
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-15 22:40 -0400
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-16 21:31 +0100
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-17 09:12 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-16 17:24 -0400
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-17 13:26 +0100
Re: Did the sort do anything? markspace <-@.> - 2011-05-15 04:56 -0700
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-15 15:12 +0100
Re: Did the sort do anything? markspace <-@.> - 2011-05-15 07:52 -0700
Re: Did the sort do anything? Michael Wojcik <mwojcik@newsguy.com> - 2011-05-18 11:14 -0400
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-18 13:02 -0400
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-20 18:49 +1200
Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-20 00:06 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-20 22:37 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-20 07:09 -0400
Re: Did the sort do anything? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-10 16:11 +0000
Re: Did the sort do anything? Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-10 21:26 +0200
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-11 21:38 +0100
Re: Did the sort do anything? Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-11 23:27 +0200
Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-05-13 07:40 -0700
Re: Did the sort do anything? Spock <spock@starfleet.ufp> - 2011-05-13 16:56 -0400
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-15 13:58 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-14 23:27 -0400
Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-11 20:40 +0200
Re: Did the sort do anything? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-05-12 10:40 -0400
Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-13 03:50 -0700
Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-05-13 07:46 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-16 14:32 +1200
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-15 19:50 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-16 17:57 +1200
Re: Did the sort do anything? "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2011-05-16 03:35 -0400
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-16 03:44 -0400
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-16 03:53 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-17 00:02 +1200
Re: Did the sort do anything? "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2011-05-16 08:05 -0400
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-17 09:12 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-16 17:32 -0400
Re: Did the sort do anything? thoolen <thoolen@tholenbot.thorium> - 2011-05-16 18:09 -0400
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-16 10:02 -0400
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-16 07:16 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-17 09:11 +1200
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-16 15:00 -0700
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-16 21:08 -0400
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-17 19:11 +1200
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-17 02:34 -0700
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-17 07:19 -0400
[OT] Naming conventions. Was: Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-17 06:52 -0700
Re: Naming conventions. Was: Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-18 01:22 -0700
Re: Naming conventions. Was: Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-18 03:42 -0700
Re: Naming conventions. Was: Re: Did the sort do anything? RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-05-18 11:53 +0100
Re: Naming conventions. Was: Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-18 13:07 -0400
Re: Naming conventions. Was: Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-18 10:37 -0700
Re: Naming conventions. Was: Re: Did the sort do anything? Heike Svensson <hsvensson.1093x1_q@hotmail.nospam.com.please> - 2011-05-19 01:29 -0400
Re: Naming conventions. Was: Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-19 08:28 +0200
Re: Naming conventions. Was: Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-19 08:50 -0400
OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-05-23 10:25 +0100
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-23 09:05 -0400
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-05-23 17:17 +0100
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-23 14:43 -0400
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? Steve Sobol <sjsobol@JustThe.net> - 2011-05-23 08:27 -0700
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-05-23 17:39 +0100
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-23 19:16 +0200
Re: OT: National stereotypes. Was Re: Naming conventions. Was: Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-23 14:47 -0400
Re: Did the sort do anything? Boojum <boojum42@gmai1.c0m> - 2011-05-18 07:19 -0400
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-20 18:46 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-20 07:10 -0400
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-17 07:16 -0400
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-17 06:56 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-20 18:46 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-20 07:11 -0400
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-20 05:00 -0700
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-20 05:20 -0700
Re: Did the sort do anything? Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-21 09:56 +1200
Re: Did the sort do anything? Lew <noone@lewscanon.com> - 2011-05-20 18:12 -0400
Re: Did the sort do anything? Patricia Shanahan <pats@acm.org> - 2011-05-20 21:26 -0700
Re: Did the sort do anything? Gheerax IV <gheerax.4@gmail.invalid> - 2011-05-17 06:58 +0000
Re: Did the sort do anything? Unitary Matrix <umatrix668@gmail.com> - 2011-05-17 00:13 -0700
Re: Did the sort do anything? markspace <-@.> - 2011-05-17 07:41 -0700
Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-05-13 07:42 -0700
Re: Did the sort do anything? Robert Klemme <shortcutter@googlemail.com> - 2011-05-13 21:28 +0200
Re: Did the sort do anything? Tom Anderson <twic@urchin.earth.li> - 2011-05-11 21:32 +0100
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