Groups > comp.lang.java.programmer > #4054

Re: Did the sort do anything?

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From	Roedy Green <see_website@mindprod.com.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: Did the sort do anything?
Date	Fri, 13 May 2011 07:40:22 -0700
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On Wed, 11 May 2011 21:38:26 +0100, Tom Anderson
<twic@urchin.earth.li> wrote, quoted or indirectly quoted someone who
said :

>Do you think hashCode is generally more efficient than compare? I would 
>have thought the opposite, because for hashCode, you have to examine all 
>an object's fields, whereas for a compareTo, you only have to examine as 
>many as it takes to find some which are different. Unless the hash is 
>cached, as in String.

The object as a whole has a hashCode.  that is just a 32 bit
operation.  The compare might end up comparing a number of long
strings char by char. HashCodes are cached.  The speed comes when it
is already computed.

In some cases you can tolerate a small rate of error. I would think
often mistaking a no-change for a change would not be catastrophic,
though the opposite normally would be. I don't think any
hashCode/checksum method could guarantee 100% accuracy.
-- 
Roedy Green Canadian Mind Products
http://mindprod.com
How long did it take after the car was invented before owners understood 
cars would not work unless you regularly changed the oil and the tires?
We have gone 33 years and still it is rare to uncover a user who 
understands computers don't work without regular backups.

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Thread

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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