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Groups > comp.lang.java.programmer > #12466

Re: Additional logging questions

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On 2/27/2012 8:48 PM, Novice wrote:
> Lew<noone@lewscanon.com>  wrote in news:jigr8v$jhh$1@news.albasani.net:
>> But wait! 'hashCode()', which is a shortcut for 'equals()' (well,
>> really for "not equals()"), doesn't know anything about those fields
>> yet! It will think objects are not equal when they really are.
>>
>> So you have to override 'hashCode()', too, using the same fields, so
>> that its result are consistent with 'equals()':
>>
>>      @Override public int hashCode()
>>      {
>>        return owner.hashCode() * 31 + color.hashCode();
>>      }
>>
> Just curious: why multiply the owner.hashCode() by 31? There's no
> significance to the 31 is there? Why not just add the two hashCodes
> together without multiplying one of them first? That would be just as
> good, right?

Actually not.

Some numbers are better than others (no multiply means 1).

You should go for a prime.

31 is often used.

But there are other good numbers.

Arne

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Additional logging questions Novice <novice@example..com> - 2012-02-27 02:02 +0000
  Re: Additional logging questions Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 21:08 -0500
    Re: Additional logging questions Novice <novice@example..com> - 2012-02-27 04:12 +0000
      Re: Additional logging questions Lew <noone@lewscanon.com> - 2012-02-26 22:13 -0800
        Re: Additional logging questions Novice <novice@example..com> - 2012-02-27 19:14 +0000
          Re: Additional logging questions Lew <noone@lewscanon.com> - 2012-02-27 12:32 -0800
          Re: Additional logging questions Lew <noone@lewscanon.com> - 2012-02-27 13:06 -0800
            Re: Additional logging questions Novice <novice@example..com> - 2012-02-28 01:48 +0000
              Re: Additional logging questions Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 20:57 -0500
                Re: Additional logging questions Lew <noone@lewscanon.com> - 2012-02-27 23:51 -0800
          Re: Additional logging questions Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 20:50 -0500
            Re: Additional logging questions Lew <noone@lewscanon.com> - 2012-02-27 23:57 -0800
        Re: Additional logging questions Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 20:45 -0500
          Re: Additional logging questions Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-02-28 01:52 -0600
            Re: Additional logging questions Arne Vajhøj <arne@vajhoej.dk> - 2012-02-28 17:20 -0500
            Re: Additional logging questions Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-28 20:26 -0400
      Re: Additional logging questions Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 20:34 -0500
  Re: Additional logging questions Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-02-27 12:36 -0800
    Re: Additional logging questions Novice <novice@example..com> - 2012-02-28 01:43 +0000

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