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Re: DeDup an ArrayList

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I am using a HashSet to DeDup, and I call
the method distinct() in analogy to the DISTINCT
keyword in SQL.

(If you go with Excel you could also call it
unique() in analogy to the corresponding
function).

So basically you need:
- 1) A hash set, either linked or not
- 2) Hash set needs a add + if not create,
      or you do a contains and then add
- 3) Hash set needs some enumeration
      into an array
- 4) Elements need hashCode() and equals()
- 5) No compareTo() for elements needed

The algorithm is pretty simple:
- add all elements to the hash set
- enumerate the elements back into a possibly shorter array

If you don't use hash set, for example a tree
you might suddently run into the problem that
your elements also need a compareTo().

If you use the java.util HashSet you incure a
great overhead, since internally HashSet is modelled
as a HashMap with a default value.

So I am using a custom light weight HashSet, without
mod count index bound checks as in java.util etc..

Bye

Roedy Green schrieb:
> This looks like trivial task, but every time I work on it, it keeps
> ballooning in complexity.
>
> I wish to deDup an ArrayList.  Any two strings equalIgnoreCase are
> considered dups. One should be removed.  The order of the items should
> be otherwise be undisturbed.
>
> Part of the trouble is removing an element from an ArrayList makes you
> lose track of where you are.
>

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Thread

DeDup an ArrayList Roedy Green <inquiry@mindprod.com> - 2016-08-04 18:35 -0700
  Re: DeDup an ArrayList Andreas Leitgeb <avl@logic.at> - 2016-08-05 02:05 +0000
    Re: DeDup an ArrayList Arne Vajhøj <arne@vajhoej.dk> - 2016-08-04 22:41 -0400
    Re: DeDup an ArrayList Lew <lewbloch@gmail.com> - 2016-08-05 15:38 -0700
      Re: DeDup an ArrayList Andreas Leitgeb <avl@logic.at> - 2016-08-06 12:10 +0000
  Re: DeDup an ArrayList Roedy Green <inquiry@mindprod.com> - 2016-08-04 19:06 -0700
    Re: DeDup an ArrayList Eric Douglas <e.d.programmer@gmail.com> - 2016-08-05 05:16 -0700
      Re: DeDup an ArrayList Andreas Leitgeb <avl@logic.at> - 2016-08-05 15:30 +0000
        Re: DeDup an ArrayList Eric Douglas <e.d.programmer@gmail.com> - 2016-08-05 10:10 -0700
          Re: DeDup an ArrayList Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-05 13:51 -0400
            Re: DeDup an ArrayList Eric Douglas <e.d.programmer@gmail.com> - 2016-08-05 12:16 -0700
              Re: DeDup an ArrayList Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-05 15:38 -0400
            Re: DeDup an ArrayList Marcel Mueller <news.5.maazl@spamgourmet.org> - 2016-08-06 00:47 +0200
    Re: DeDup an ArrayList Arne Vajhøj <arne@vajhoej.dk> - 2016-08-05 09:02 -0400
  Re: DeDup an ArrayList Jan Burse <janburse@fastmail.fm> - 2016-08-05 12:52 +0200
    Re: DeDup an ArrayList Jan Burse <janburse@fastmail.fm> - 2016-08-05 12:53 +0200
      Re: DeDup an ArrayList Jan Burse <janburse@fastmail.fm> - 2016-08-05 13:10 +0200
        Re: DeDup an ArrayList Jan Burse <janburse@fastmail.fm> - 2016-08-13 12:26 +0200
  Re: DeDup an ArrayList Daniel Pitts <usenet@coloraura.com> - 2016-08-05 08:37 -0700
    Re: DeDup an ArrayList Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-08-05 08:58 -0700
      Re: DeDup an ArrayList Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-08-05 09:47 -0700
        Re: DeDup an ArrayList Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-08-05 19:56 -0700
        Re: DeDup an ArrayList Daniel Pitts <usenet@coloraura.com> - 2016-08-06 09:18 -0700
  Re: DeDup an ArrayList Marcel Mueller <news.5.maazl@spamgourmet.org> - 2016-08-06 01:04 +0200
  Re: DeDup an ArrayList Roedy Green <inquiry@mindprod.com> - 2016-08-05 16:31 -0700

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