Sorting String with non-western characters

Question

I wanted to print sorted Polish names of all available languages.

import java.util.*;

public class Tmp
{
  public static void main(String... args)
  {
    Locale.setDefault(new Locale("pl","PL"));
    Locale[] locales = Locale.getAvailableLocales();
    ArrayList<String> langs = new ArrayList<String>();
    for(Locale loc: locales) {
      String  lng = loc.getDisplayLanguage();
      if(!lng.trim().equals("") && ! langs.contains(lng)){
        langs.add(lng);
      }
    }
    Collections.sort(langs);
    for(String str: langs){
      System.out.println(str);
    }
  }
}

Unfortunately I have issue with the sorting part. The output is:

:
:
kataloński
koreański
litewski
macedoński
:
:
węgierski
włoski
łotewski

Unfortunately in Polish ł comes after l and before m so the output should be:

:
:
kataloński
koreański
litewski
łotewski
macedoński
:
:
węgierski
włoski

How can I accomplish that? Is there an universal non-language-dependent method (say I now want to display this and sort in another language with another sorting rules).

Answer 1

try

Collections.sort(langs, Collator.getInstance(new Locale("pl", "PL")));

it will produce

...
litewski
łotewski
...

see Collator API for details

Answer 2

You should pass a Collator to the sort method:

// sort according to default locale
Collections.sort(langs, Collator.getInstance());

The default sort order is defined by the Unicode codepoints in the string, and that's not the correct alphabetical order in any language.

Answer 3

Have a look at java.text.Collator.newInstance(Locale). You need to supply the Polish locale in your case. Collators implement the Comparator interface, so you can use that in sort APIs and in sorted datastructures like TreeSet.