Groups > comp.lang.java.programmer > #35198

Re: DeDup an ArrayList

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From	Arne Vajhøj <arne@vajhoej.dk>
Newsgroups	comp.lang.java.programmer
Subject	Re: DeDup an ArrayList
Date	Thu, 4 Aug 2016 22:41:18 -0400
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On 8/4/2016 10:05 PM, Andreas Leitgeb wrote:
> Roedy Green <inquiry@mindprod.com> wrote:
>> 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.
>
> Copy to a LinkedHashMap (using the toUpperCase()'d string as key, and
> the original String as value), and finally copy back to a new ArrayList...
>
> The LinkedHashMap will take care of maintaining the ordering, except
> of course, where dups are left out.

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.stream.Collectors;

public class ListDeDup {
	public static void main(String[] args) {
		List<String> lst = new ArrayList<>();
		lst.add("Aa");
		lst.add("Bb");
		lst.add("Cc");
		lst.add("cC");
		lst.add("bB");
		lst.add("aA");
		System.out.println(lst);
		List<String> res = lst.stream().collect(Collectors.toMap(o -> 
o.toLowerCase(), o -> o, (o1,o2) -> o1, 
LinkedHashMap::new)).values().stream().collect(Collectors.toList());
		System.out.println(res);
	}
}

> Not sure if hashing on the uppercase version of a String is strictly
> equivalent to pairwise equalIgnoreCase, though. Maybe not, maybe close
> enough, maybe exactly same...  The performance advantage (from n-squared
> to roughly n) might be worth a little slack in some corner cases.

There is always the "Turkish problem", but ...

Arne

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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