Sort a List of String array objects

Question

How can i Sort a list of String array objects alphabetically.

I Set my List as follows:

List CurrentRankingsList = rankings.getRankings();

I have a List of String objects like this:

[["Dwayne","5"], ["Bill","4"], ["James","3"], ["Sally","3"]]

How can i sort this list by the Names, alphabetically whilst maintaining the List structure eg [["Bill","4"], ["Dwayne","5"], ["James","3"], ["Sally","3"]] I've tried the following but list is not getting sorted correctly

      (Updated code from original question )    
           Collections.sort(CurrentRankingsList, new Comparator<Rankable>() 
            {
            @Override
            public int compare(Rankable o1, Rankable o2) {
            // TODO Auto-generated method stub
            String testo1=o1.getObject().toString();
            String testo2=o2.getObject().toString();
            int x = o1.getObject().toString().compareTo(o2.getObject().toString());
            return  o1.getObject().toString().compareTo(o2.getObject().toString());
            }
        }) ;

On debugging the compare we get a Paul (o1.GetObject.ToString) vs Nathan(o2.GetObject.ToString)

stackoverflow.com/questions/4907683/… You will get the idea from here — Aroon
– Aroon, Commented Dec 12, 2013 at 19:39
This looks very similar to JSON if you just adjust the format. See here stackoverflow.com/questions/15855548/… — user2591612
– user2591612, Commented Dec 12, 2013 at 19:42

Sage · Accepted Answer · 2013-12-12 19:25:54Z

2

How can i Sort a list of String array objects alphabetically.

Declare list or any collection with type: ArrayList<String[]>, List<String[]> otherwise the Collection will be regarded as raw type and we will face run-time error overhead for type unsafe operation.

You will need to pass String[] as type to Comparator

 Collections.sort(CurrentRankingsList, new Comparator<String[]>() 
 {
    @Override
    public int compare(String[] o1, String[] o2) {
        // TODO Auto-generated method stub
                return o1[0].compareTo(o2[0]);
     }
 }) ;

Assuming that CurrentRankingsList is the list of array string.

For such case, more cleaner approach would be to declare a class for example, Player with two attribute(name, rank) and then sort based upon the instance of that class.

 class Player
 {
    String name;
    int rank;

     // your other code with constructor and getter, setter method    
  }

 ArrayList<Player>currentRankingsList = new ArrayList<>();

 Collections.sort(CurrentRankingsList, new Comparator<Player>() 
 {
    @Override
    public int compare(Player o1, Player o2) {
        // TODO Auto-generated method stub
                return o1.getName().compareTo(o2.getName());
     }
 }) ;

edited Dec 12, 2013 at 19:25

answered Dec 12, 2013 at 19:09

Sage

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6 Comments

user2336315 Over a year ago

I think CurrentRankingsList is either a List of List<String> or a List of String[].

Sage Over a year ago

I think you might be right but the OP's mentioning about How can i sort this list by the Names is quite confusing :)

user2336315 Over a year ago

That wouldn't change your code too much ^^ public int compare(String[] o1, String []o2) {return o1[0].compareTo(o2[0]);}

Fearghal Over a year ago

Hey, thanks for the answer. 1st one error'd because we were comparing an object to a string. So we tried second and debugged at the compare and see that Paul vs Nathan returns a 2. The list is then not sorted correctly, i think it does some sorting which appears random.

Sage Over a year ago

@Fearghal, could you please rephrase. Are you saying the proposed approach using Comparator<String[]> isn't working ?

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