Implementing comparable for a TreeMap

Question

I'm trying to create a League of Players which is ordered by the player grade, but the comparism method (compareTo) doesn't seem to be getting called. The following list should be displayed in grade order
RANK LIST
950 Alactaga
1000 Aragorn
1000 Black Jack II
950 Brius
1100 Fitzchev
1150 Heraldo
950 Horace
900 Killer Giraffe
I have 3 main classes involved: Player, Players, League
public class Player implements Comparable {
     private static final int START_GRADE = 1000;
     private String name;
     private int grade;
      * Constructor
      * Note that the constructor is private to ensure that
      * only one unique version of each player can exist.
     private Player(String name) {
          this.name = name;
          this.grade = START_GRADE;
     public int compareTo(Object o) {
               System.out.println("Comparing!!");
             Player n = (Player)o;
             int gradeComp = new Integer(grade).compareTo(new Integer(n.grade));
             return gradeComp;
      * Factory method for creating a new player
     public static Player create(String name) {
          return new Player(name);
public class Players extends TreeMap {
      * Constructor
     public Players() {
          loadPlayers();
      * Load the players
      * These could come from a file or a database.
     private void loadPlayers() {
          // Some hard-coded stuff for testing
          this.put("Black Jack II", Player.create("Black Jack II"));
          this.put("Fitzchev", Player.create("Fitzchev"));
          this.put("Brius", Player.create("Brius"));
     public Player getNamed(String name) {
          return (Player) get(name);
public class League extends Players {
     private static final int DELTA = 50;
      * Main routine for recalculating rankings based on a given game
     public void scoreGame(Game game) {
     }I followed the following tutorial item to get me started:
http://java.sun.com/docs/books/tutorial/collections/interfaces/order.html
Thanks for any help!

Answer 1

Thanks for the help. The toString() function of the League class now begins as follows:
      * Create a string version of the ranked list
     public String toString() {
          String rankListString = "";
          rankListString += "RANK LIST\n";
          rankListString += "---------\n";
          Collection players = this.values();
          Players[] playersArray = (Players[]) players.toArray();
          Comparator myComparator = new Comparator() {
               public int compare(Object o1, Object o2) {
                    int comp;
                    System.out.println("Comparing!!");
                    Player p1 = (Player)o1;
                    Player p2 = (Player)o2;
                    if (p1.getGrade() < p2.getGrade()) {
                         comp = -1;     
                    else if (p1.getGrade() > p2.getGrade()) {
                         comp = 1;
                    else {
                         comp = 0;
                    return comp;
          Arrays.sort(playersArray, myComparator);At the moment though I have a ClassCastException on the following line:
Players[] playersArray = (Players[]) players.toArray();          java.lang.ClassCastException
     at core.League.toString(League.java:65)
     at java.lang.String.valueOf(Unknown Source)
     at java.io.PrintStream.print(Unknown Source)
     at java.io.PrintStream.println(Unknown Source)
     at main.Grape.main(Grape.java:37)
Exception in thread "main"
I'm still a bit of a newbie as you can see. Any help would be appreciated. Thanks!