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Groups > comp.lang.java.programmer > #17753

Re: hashCode

From "Lew" <lew@1:261/38.remove-m2z-this>
Subject Re: hashCode
Message-ID <5027F2CA.56698.calajapr@time.synchro.net> (permalink)
Newsgroups comp.lang.java.programmer
References <5027F2C9.56692.calajapr@time.synchro.net>
Date 2012-08-12 18:58 +0000
Organization tds.net

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  To: =?UTF-8?B?QXJuZSBWYWpow7hq?=
From: Lew <noone@lewscanon.com>

Arne Vajh-,j wrote:
> Lew wrote:
>> Jan Burse wrote:
>>> Maybe it would make sense to spell out what the contract
>>> for hashCode() is. Well the contract is simply, the
>>> following invariant should hold:
>>>
>>>     /* invariant that should hold */
>>>     if a.equals(b) then a.hashCode()==b.hashCode()
>>
>> True, but if you read the specification for 'hashCode()' fully, that is
>> not the entire contract, only the compiler-enforceable part of it.
>>
>> The entire specification requires that as much as feasible, the 'Object'
>> implementation distinguish distinct instances, and that the method
>> generally support 'HashMap', which promises O(1) 'get()' and 'put()'
>> with a "proper" (i.e., compliant) 'hashCode()'.
>
> Two wrong statements.
>
> It says that the method is defined to support HashMap
>
> And HashMap does not guarantee O(1) with a correct
> hashCode - it guarantee that for one that return
> good distributed values.

Granted.

--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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hashCode "bob smith" <bob.smith@1:261/38.remove-t9h-this> - 2012-08-10 18:39 +0000
  Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-t9h-this> - 2012-08-10 18:39 +0000
    Re: hashCode "markspace" <markspace@1:261/38.remove-t9h-this> - 2012-08-10 18:39 +0000
      Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-t9h-this> - 2012-08-10 18:39 +0000
        Re: hashCode "rossum" <rossum@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
  Re: hashCode "Eric Sosman" <eric.sosman@1:261/38.remove-t9h-this> - 2012-08-10 18:39 +0000
    Re: hashCode "bob smith" <bob.smith@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
      Re: hashCode "Lew" <lew@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
          Re: hashCode "Lew" <lew@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
            Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
              Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
                Re: hashCode "Eric Sosman" <eric.sosman@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
                Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Eric Sosman" <eric.sosman@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Lew" <lew@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
          Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Robert Klemme" <robert.klemme@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
          Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-nlb-this> - 2012-08-13 18:36 +0000
            Re: hashCode "Robert Klemme" <robert.klemme@1:261/38.remove-nlb-this> - 2012-08-13 18:36 +0000
              Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-fzq-this> - 2012-08-20 18:58 +0000
              Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-fzq-this> - 2012-08-20 18:58 +0000
      Re: hashCode "Patricia Shanahan" <patricia.shanahan@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Joshua Cranmer" <joshua.cranmer@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
        Re: hashCode "Patricia Shanahan" <patricia.shanahan@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
          Re: hashCode "Eric Sosman" <eric.sosman@1:261/38.remove-6fd-this> - 2012-08-12 20:00 +0000
            Re: hashCode "Patricia Shanahan" <patricia.shanahan@1:261/38.remove-6fd-this> - 2012-08-12 20:00 +0000
          Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-nlb-this> - 2012-08-13 18:36 +0000
        Re: hashCode "Jan Burse" <jan.burse@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
  Re: hashCode "Roedy Green" <roedy.green@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
    Re: hashCode "Lew" <lew@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
      Re: hashCode "Roedy Green" <roedy.green@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Joerg Meier" <joerg.meier@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
          Re: hashCode "Mike Winter" <mike.winter@1:261/38.remove-ya-this> - 2012-08-11 19:19 +0000
        Re: hashCode "Peter Duniho" <peter.duniho@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Jan Burse" <jan.burse@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "rossum" <rossum@1:261/38.remove-ya-this> - 2012-08-11 19:19 +0000
    Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
      Re: hashCode "Eric Sosman" <eric.sosman@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
        Re: hashCode "Arne Vajhøj" <arne.vajhøj@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
  Re: hashCode "Jan Burse" <jan.burse@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
    Re: hashCode "Jan Burse" <jan.burse@1:261/38.remove-pjg-this> - 2012-08-11 18:17 +0000
    Re: hashCode "Lew" <lew@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Lew" <lew@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
        Re: hashCode "Lew" <lew@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
    Re: hashCode "Jan Burse" <jan.burse@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Jan Burse" <jan.burse@1:261/38.remove-m2z-this> - 2012-08-12 18:58 +0000
      Re: hashCode "Lew" <lew@1:261/38.remove-6fd-this> - 2012-08-12 20:00 +0000
        Re: hashCode "Arne Vajhøj" <������
høj@1:261/38.remove-nlb-this> - 2012-08-13 18:36 +0000

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