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From: Daniel Pitts <usenet@coloraura.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: DeDup an ArrayList
Date: Fri, 5 Aug 2016 08:37:36 -0700
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On 8/4/16 6:35 PM, Roedy Green 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.
>

Stream version:

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
import java.util.*;
import java.util.stream.Collectors;

public class Dedup {

     public static void main(String[] args) {
         final List<String> list = new ArrayList<>(Arrays.asList(
             "First",
             "Second",
             "first",
             "Third",
             "third",
             "second",
             "Last"));


         final List<String> result =
             list.stream()
                 .collect(
                     Collectors.groupingBy(
                         String::toLowerCase,
                         LinkedHashMap<String, List<String>>::new,
                         Collectors.toList()
                     )
                 )
                 .entrySet()
                 .stream()
                 .map(Map.Entry::getValue)
                 .map(l -> l.get(0))
                 .collect(Collectors.toList());

         result.forEach(System.out::println);
     }
}


************************************************************************************************

In-place non-stream version:

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=


import java.util.*;

public class Dedup {

     public static void main(String[] args) {
         final List<String> list = new ArrayList<>(Arrays.asList(
             "First",
             "Second",
             "first",
             "Third",
             "third",
             "second",
             "Last"));

         final Set<String> exists = new HashSet<>();
         for (final Iterator<String> i = list.iterator(); i.hasNext();) {
             if (!exists.add(i.next().toLowerCase())) {
                 i.remove();
             }
         }

         list.forEach(System.out::println);
     }
}

************************************************************************************************