如何在类对象属性的hashmap上使用可比性

Question

我有一个足球桌，我试图按赢得的比赛排序。

class TeamStandings implements Comparable<TeamStandings>{
    protected int matchesPlayed = 0;
    protected int won = 0;
    protected int draw = 0;
    protected int loss = 0;
    protected int goalsScored = 0;
    protected int goalsConceded = 0;
    protected int goalDifference = 0;
    protected int points = 0;

    @Override
    public int compareTo(TeamStandings other){
        // compareTo should return < 0 if this is supposed to be
        // less than other, > 0 if this is supposed to be greater than 
        // other and 0 if they are supposed to be equal

        //System.out.println(this.won + " " + other.won + " " + Integer.valueOf(this.won).compareTo(Integer.valueOf(other.won)));
        return Integer.valueOf(this.won).compareTo(Integer.valueOf(other.won));

    }
}

private static HashMap sortByValues(HashMap map) { 
    List list = new LinkedList(map.entrySet());
    // Defined Custom Comparator here
    Collections.sort(list, new Comparator() {
        public int compare(Object o1, Object o2) {

            System.out.println(((Comparable) ((Map.Entry) (o1)).getValue()).compareTo(((Map.Entry) (o2)).getValue()));
            return ((Comparable) ((Map.Entry) (o1)).getValue())
                    .compareTo(((Map.Entry) (o2)).getValue());          
        }
    });

    // Here I am copying the sorted list in HashMap
    // using LinkedHashMap to preserve the insertion order
    HashMap sortedHashMap = new LinkedHashMap();
    for (Iterator it = list.iterator(); it.hasNext();) {
        Map.Entry entry = (Map.Entry) it.next();
        sortedHashMap.put(entry.getKey(), entry.getValue());
        //System.out.println(entry.getKey());
    } 
    return sortedHashMap;
}

不知什么原因，我无法把桌子整理好。它只是停留在未排序的顺序中。我认为这与collection.sort位置的sortbyvalues函数有关。

你知道如何使用类中的won值对HashMap进行排序吗？

public void printTable(){

    Map<String, TeamStandings> sortedTable = sortByValues(this.table);

    System.out.println("Group: " + this.groupLetter);
    System.out.println("Team" 
            + "\t" + "MP"
            + "\t" + "W"
            + "\t" + "D"
            + "\t" + "L"
            + "\t" + "GS"
            + "\t" + "GC"
            + "\t" + "GD"
            + "\t" + "P");

    //Iterator<Map.Entry<String, TeamStandings>> iterator = this.table.entrySet().iterator() ;
    Iterator<Map.Entry<String, TeamStandings>> iterator = sortedTable.entrySet().iterator() ;

    while(iterator.hasNext()){
        Map.Entry<String, TeamStandings> team = iterator.next();
        System.out.println(team.getKey() 
                + "\t" + team.getValue().matchesPlayed
                + "\t" + team.getValue().won
                + "\t" + team.getValue().draw
                + "\t" + team.getValue().loss
                + "\t" + team.getValue().goalsScored
                + "\t" + team.getValue().goalsConceded
                + "\t" + team.getValue().goalDifference
                + "\t" + team.getValue().points);
    }
}

谢谢

    List list = new LinkedList(map.entrySet());
    // Defined Custom Comparator here
    Collections.sort(list, new Comparator() {
        public int compare(Object o1, Object o2) {

            System.out.println(((Comparable) ((Map.Entry) (o1)).getValue()).compareTo(((Map.Entry) (o2)).getValue()));
            return ((Comparable) ((Map.Entry) (o1)).getValue())
                    .compareTo(((Map.Entry) (o2)).getValue());          
        }
    });

return Integer.valueOf(this.won).compareTo(Integer.valueOf(other.won)) * -1;

感谢@Justin和@Falsarella。

Answer 1

我不认为HashMap维护插入顺序。试试树图。或AVolpe建议的LinkedHashmap

http://docs.oracle.com/javase/7/docs/api/java/util/treemap.html