Re: hashCode

Discussion in 'Java' started by Arne Vajhøj, Aug 13, 2012.

  1. Arne Vajhøj

    Arne Vajhøj Guest

    To: Robert Klemme
    From: "Arne Vajhoj" <arne.vajhoj@1:261/38.remove-nlb-this>

    To: Robert Klemme
    From: Arne Vajhoj <>

    On 8/12/2012 11:06 AM, Robert Klemme wrote:
    > On 11.08.2012 01:27, Arne Vajhoj 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


    More or less.

    > - and that makes it broken.


    This thread started about whether it is correct. The term correct has a very
    specific meaning in programming and that always return 1 code is correct.

    Now you talk about broken. If broken means not good, then you are right. If
    broken means not correct, then you are wrong. I suspect that broken is not very
    well defined.

    > 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.


    It disable the entire hashing functionality and a HashMap get characteristics
    of ArrayList.

    But the code should actually work.

    Arne

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    Arne Vajhøj, Aug 13, 2012
    #1
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