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Groups > comp.lang.java.programmer > #9739
| From | Eric Sosman <esosman@ieee-dot-org.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Did the sort do anything? |
| Date | 2011-11-07 07:11 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <j98hu1$aj8$1@dont-email.me> (permalink) |
| References | <4d8fb7l8qb1g820cphr4fh447a9uitlddj@4ax.com> |
On 11/7/2011 4:27 AM, Roedy Green wrote:
> What is the easiest way to determine if a sort actually changed the
> order?
>
> I run into this in two situations.
>
> 1. do I really need to sort in cases when the data are most likely
> already in order? (perhaps just sorting is as fast as trying to bypass
> it most of the time).
>
> 2. did the sort change anything. Do I have to commit the changed order
> to disk?
>
> The obvious solution to (1) is to pairwise compare array exported from
> the collection before the sort.
>
> The obvious solution to (2) is compare corresponding elements in
> arrays exported before and after the sort with the comparator, or use
> (1).
Post-sort order check won't do: The sort might have interchanged
two different objects with equal keys.
> Can you do better than that?
>
> Oracle might add a method isInOrder and/or didOrderChange. The various
> sort methods are static, so their is no natural place to put them.
The sort method itself could return a value to indicate that it
changed the order, didn't change the order, or is unable to say for
sure whether it did or didn't. (Some algorithms -- Heapsort, for
example, or a straight merge -- don't offer an easy way to tell whether
something happened.)
--
Eric Sosman
esosman@ieee-dot-org.invalid
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Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-07 01:27 -0800
Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-07 02:20 -0800
Re: Did the sort do anything? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-11-07 11:21 +0000
Re: Did the sort do anything? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-11-07 10:49 +0000
Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-07 02:58 -0800
Re: Did the sort do anything? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-07 07:11 -0500
Re: Did the sort do anything? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-11-07 08:30 -0600
Re: Did the sort do anything? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-07 21:03 -0500
Re: Did the sort do anything? markspace <-@.> - 2011-11-07 07:48 -0800
Re: Did the sort do anything? dagon@dagon.net (Dagon) - 2011-11-07 12:50 -0800
Re: Did the sort do anything? Cindy <c.thurston@frell.okb.uwa.edu> - 2011-11-07 22:02 -0500
Re: Did the sort do anything? Cindy <c.thurston@frell.okb.uwa.edu> - 2011-11-07 22:22 -0500
Re: Did the sort do anything? Arne Vajhøj <arne@vajhoej.dk> - 2011-11-07 17:42 -0500
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