sort and group a java collection

Question

I have an object which has a name and a score. I would like to sort a collection of such objects so that they are grouped by name and sorted by maximum score in each group (and

Answer 1

Yes Go for Comparator

Give first preference to name in comparison and then to score. it will be grouped up with sorted score also

    List scores = new ArrayList();
    scores.add(new Score("a", 58));
    scores.add(new Score("a", 10));
    scores.add(new Score("b", 165));
    scores.add(new Score("a", 1));
    scores.add(new Score("b", 1658));
    scores.add(new Score("c", 1));
    scores.add(new Score("c", 10));
    scores.add(new Score("c", 0));

    Collections.sort(scores, new Comparator() {

        public int compare(Score o1, Score o2) {
            if (o1.getName().compareTo(o2.getName()) == 0) {
                return o2.getScore() - o1.getScore();
            } else {
                return o1.getName().compareTo(o2.getName());
            }
        }
    });
    System.out.println(scores);

Update

As Chris pointed out.

import java.util.*;

/**
 *
 * @author Jigar
 */
class Score {

    private String name;
    private List scores;

    public Score() {
    }

    public Score(String name, List scores) {
        this.name = name;
        this.scores = scores;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List getScores() {
        return scores;
    }

    public void setScores(List scores) {
        this.scores = scores;
    }

    @Override
    public String toString() {
        return name + " , " + scores + "\n";
    }
}

public class ScoreDemo { 

    public static void main(String[] args) {
        List scores = new ArrayList();


        List lstA = new ArrayList();
        lstA.add(3);
        lstA.add(9);
        lstA.add(7);
        Collections.sort(lstA);
        Collections.reverse(lstA);

        List lstB = new ArrayList();
        lstB.add(10);
        lstB.add(8);
        lstB.add(3);
        Collections.sort(lstB);
        Collections.reverse(lstB);

        List lstC = new ArrayList();
        lstC.add(8);
        lstC.add(3);
        Collections.sort(lstC);
        Collections.reverse(lstC);


        scores.add(new Score("a", lstA));
        scores.add(new Score("b", lstB));
        scores.add(new Score("c", lstC));





        Collections.sort(scores, new Comparator() {

            public int compare(Score o1, Score o2) {
                return o2.getScores().get(0).compareTo(o1.getScores().get(0));
            }
        });
        System.out.println(scores);

    }
}

• Here is working ideone demo

• UPDATE: Here is working ideone demo