Cannot sort my ArrayList of String

Question

I'm tring to sort an arraylist of String alphabetically, I tried everything, from the simple way :

List<String> theList = new ArrayList<String>();
theList.add("silex");theList.add("soliton");
theList.add("snake");theList.add("supracanon");
Collections.sort(theList);

To something more exotic :

List<String> theList = new ArrayList<String>();
theList.add("silex");theList.add("soliton");
theList.add("snake");theList.add("supracanon");
Collections.sort(
  theList, 
  new Comparator<String>() 
  {
    public int compare(String lhs, String rhs) 
    {
      return lhs.compareTo(rhs);
    }
  }
);

But nothing works, what am I doing wrong? thanks.

ps : I'm looking at the content of the resulting ArrayList like this :

for (String temp:listeProduitPredit){
            System.out.println(temp);
        }

the content of the list does not change before and after the sorting process.

============================================================================= Allright, this is the actual code, I have an EJB doing database access, one of it's methods is returning me list of string.

tha list of strings is suposed to be ordered like in the dictionnary (alphabetically) however the 'Collections.sort(rList)' does nothing (input = output)

public List<String> rechercherListeDeProduitCommencantPar(Integer gammeId, Integer familleId, String debutProduit) {
    Criteria c = HibernateUtil.getSessionFactory().getCurrentSession().createCriteria(Produit.class, "p");
    c.createAlias("p.famille", "f").createAlias("f.gamme", "g");

    if (gammeId != null) {
        c.add(Restrictions.eq("g.id", gammeId));
    }
    if (familleId != null) {
        c.add(Restrictions.eq("f.id", familleId));
    }
    if (!debutProduit.equals("")) {
        c.add(Restrictions.like("p.designation", debutProduit+"%"));
    }

    //getting only the interesting intels (product's name)
    List<String> rList = new ArrayList<String>();
    List<Produit> pList = c.list();
    for (Produit p : pList){
        rList.add(p.getDesignation());
    }
    Collections.sort(rList);
    return rList;
}

this is running on a Jboss AS 5.1 server, I tested it by using a for before and after, the list is not being sorted alphabetically but it is indeed being modified a little:

18:44:07,961 INFO  [STDOUT] Before=========
18:44:07,961 INFO  [STDOUT] SUMO VIE
18:44:07,961 INFO  [STDOUT] soliton
18:44:07,961 INFO  [STDOUT] snake
18:44:07,961 INFO  [STDOUT] SupraCanon
18:44:07,961 INFO  [STDOUT] Segolene
18:44:07,961 INFO  [STDOUT] silex
18:44:07,962 INFO  [STDOUT] After=========
18:44:07,962 INFO  [STDOUT] SUMO VIE
18:44:07,962 INFO  [STDOUT] Segolene
18:44:07,962 INFO  [STDOUT] SupraCanon
18:44:07,962 INFO  [STDOUT] silex
18:44:07,962 INFO  [STDOUT] snake
18:44:07,962 INFO  [STDOUT] soliton

How exactly does it "not work"? How are you running that code and how are you examining the result? See sscce.org — Michael Borgwardt
– Michael Borgwardt, Commented Aug 9, 2012 at 16:21
I've tried your code, and it looks fine, as seen here: ideone.com/lrUDO. — João Silva
– João Silva, Commented Aug 9, 2012 at 16:24
@assylias: It's not sorted, note that OP is inserting two elements per line. — João Silva
– João Silva, Commented Aug 9, 2012 at 16:25
@Eildosa: most likely the error is in the code you are still now showing us. Again: sscce.org — Michael Borgwardt
– Michael Borgwardt, Commented Aug 9, 2012 at 16:30
Show us the output you got and the output you expected, or we can't help. — Louis Wasserman
– Louis Wasserman, Commented Aug 9, 2012 at 16:30

davidfmatheson · Accepted Answer · 2012-08-09 17:06:53Z

3

Your "after" array is sorted alphabetically:

18:44:07,962 INFO  [STDOUT] After=========
18:44:07,962 INFO  [STDOUT] SUMO VIE
18:44:07,962 INFO  [STDOUT] Segolene
18:44:07,962 INFO  [STDOUT] SupraCanon
18:44:07,962 INFO  [STDOUT] silex
18:44:07,962 INFO  [STDOUT] snake
18:44:07,962 INFO  [STDOUT] soliton

It's just that upper-case letters take precedence.

EDIT: If you want a case-insensitive sort, use:

theList.add("SUMO VIE");theList.add("soliton");
theList.add("snake");theList.add("supracanon");
Collections.sort(theList, String.CASE_INSENSITIVE_ORDER);

as suggested by Natix below.

edited Aug 9, 2012 at 17:06

answered Aug 9, 2012 at 16:54

davidfmatheson

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2 Comments

Heetola Over a year ago

Oh god how could I not see that xD?! thanks. yes I'd like to sort them case-insensitively. I used the exotic snipet and added toLowerCase() in the return but if you have a better suggestion I'll gladly take it.

keuleJ Over a year ago

String.compareTo() uses the unicode code for ordering. You should use a Collator instead.

Natix · Accepted Answer · 2012-08-09 16:57:31Z

2

Upper case characters come before lowercase characters.

"SUMO VIE".compareTo("Segolene") < 0

To sort your string list in case insensitive manner, you can use this comparator:

Collections.sort(rList, String.CASE_INSENSITIVE_ORDER);

answered Aug 9, 2012 at 16:57

Natix

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