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From "Juozas Baliuka" <bali...@centras.lt>
Subject Re: [Collections][SUBMIT] ReferenceMap...take 3...
Date Sat, 20 Jul 2002 07:13:17 GMT
Hi,
I think it is good idea to have interface HashFunction.
for "Autoincrement"  can be used some "good" hash function to make
keys "random".
And I think it is good to add "maxValue" parameter, it can help for some
hash functions.

//return value must be in [ - maxValue, maxValue ]
 int translateHashCode(int hashCode, int maxValue);



> I'm a big fan of Knuth's, but I don't actually have any of the
> books mentioned on my shelves.  I'll probably go get the Intro
> to Algorithms one.  I actually went out and bought _Effective
> Java_ because Stephen Coulbourne kept invoking it...I never
> realized membership on this list would be so expensive!
>
> Meanwhile, I'm wondering if it's worth allowing users to
> specify their own hash functions:
>
> public interface HashFunction {
>
>     int translateHashCode(int hashCode);
>
>
>     HashFunction DEFAULT = new HashFunction() {
>         public int translateHashCode(int hash) {
>             return hash * -127;
>         }
>     };
>
>     HashFunction IDEAL = new HashFunction() {
>         public int translateHashCode(int hash) {
>             return (somePrime - 2 - hash) % (somePrime - 2);
>         }
>     };
> }
>
> Then SequencedHashMap and ReferenceMap could allow users to specify
> a HashFunction in their constructors.
>
> Thoughts?
>
> -Paul
>
>
>
>
> > -----Original Message-----
> > From: Juozas Baliuka [mailto:baliuka@centras.lt]
> > Sent: Friday, July 19, 2002 2:55 PM
> > To: Jakarta Commons Developers List
> > Subject: Re: [Collections][SUBMIT] ReferenceMap...take 3...
> >
> >
> > Books by Don Knuth are very good, but I don't have them at home
> > http://www-cs-faculty.stanford.edu/~knuth/gk.html
> >
> >
> > > On Fri, 19 Jul 2002, Jack, Paul wrote:
> > > > Hm.  I couldn't really find my way around the above page.
> >  It definitely
> > > > has a lot of good stuff but it's organized chronologically, so I
> > couldn't
> > > > find specific things related to hash functions... I'll
> > keep looking.
> > >
> > > My Intro to Algorithms book lists a "Multiplication Method"
> > that should
> > > work well.  Don't have the book with me at the moment, but
> > I'll try to
> > > summarize tonight...
> > >
> > > btw, if you don't own it already, I highly recommend the book:
> > > http://www.amazon.com/exec/obidos/ASIN/0262032937
> > >
> > > regards,
> > > michael
> > >
> > >
> > >
> > >
> > > --
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> > >
> >
> >
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