java - 如何在类对象属性的 HashMap 上使用可比性

Question

我有一个足球表，我正在尝试按赢得的比赛进行排序。

我有一个类实现比较并查看赢得的属性。这似乎返回了正确的值(1、-1 或 0)。

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));

    }
}

此排序函数应返回排序后的 HashMap 。 HashMap 以团队名称作为键，以 teamstands 类的实例作为值。

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;
}

HashMap 排序表，采用团队名称字符串和包含获胜、失败比赛等的团队排名类对象。

由于某种原因，我无法对表格进行排序。它只是保持未排序的顺序。我相信这与 collection.sort 位置的 sortbyvalues 函数有关。

有什么想法可以使用我的类中的赢取值来对 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

戴夫

编辑:

我认为这与这段代码有关，因为我打印了列表条目，但它们没有排序:

    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());          
        }
    });

我将代码改回了最初发布的代码，这与 LinkedList 或 LinkedHashMap 无关，代码实际上一直有效，只是按升序排序。这对于足球联赛表来说显然是不正确的。

编辑:

修复方法是添加此处显示的 * -1:

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

感谢@Justin 和@falsarella。

Answer 1

显然，正如 @Justin 评论的那样，输出已排序，但按升序顺序排列:

0, 1, 2, 3

如果您希望按后代顺序排列，只需更改从compareTo方法返回的整数符号即可:

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