如何排序对象的ArrayList [英] How to sort Arraylist of objects

问题描述

我有ArrayList中，这containst橄榄球队（班队）。球队有观点，我想通过点数对它们进行排序。

I have ArrayList, which containst football teams (class Team). Teams have points and i want to sort them by number of points.

 public class Team {
     private int points;
     private String name;

     public Team(String n)
     {
         name = n;
     }

     public int getPoints
     {
         return points;
     }

     public void addPoints(boolean win)
 {
            if (win==true)
            {
    points = points + 3;
            }

            else if (win==false)
            {
            points = points + 1;
            }

}
 //...
 }

主类：

 List<Team> lteams = new ArrayList<Team>;

 lteams.add(new Team("FC Barcelona"));
 lteams.add(new Team("Arsenal FC"));
 lteams.add(new Team("Chelsea"));

 //then adding 3 points to Chelsea and 1 point to Arsenal

 lteams.get(2).addPoints(true);
 lteams.get(1).addPoints(false);

 //And want sort teams by points (first index with most points). 

我做比较。

 public class MyComparator implements Comparator<Team> {


    @Override
    public int compare(Team o1, Team o2) {
        if (o1.getPoints() > o2.getPoints())
         {
             return 1;
         }
        else if (o1.getPoints() < o2.getPoints())
        {
            return -1;
        }
        return 0;    
    } 

}

现在我想用它（在主类）

now I wanna use it (in main class)

 Colections.sort(lteams, new MyComparator());

我要见：

1. 切尔西


2. 阿森纳


3. 巴塞罗那

不过，这并不排序。

推荐答案

来源：<一个href=\"http://stackoverflow.com/questions/2535124/how-to-sort-an-arraylist-of-objects-by-a-property\">Here

您可以使用<一个href=\"http://java.sun.com/javase/6/docs/api/java/util/Collections.html#sort%28java.util.List%29\"><$c$c>Collections.sort使用自定义的<$c$c>Comparator<Team>.

    class Team {
        public final int points;
        // ...
    };

    List<Team> players = // ...

    Collections.sort(players, new Comparator<Team>() {
        @Override public int compare(Team p1, Team p2) {
            return p1.points- p2.points;
        }

    });

另外，你可以让团队实施 <$c$c>Comparable<Team>.这个定义的的的自然所有的团队对象排序。使用比较是在不同的实现更加灵活的可以按姓名，年龄等订购。

Alternatively, you can make Team implementsComparable<Team>. This defines the natural ordering for all Team objects. Using a Comparator is more flexible in that different implementations can order by name, age, etc.

• Java:什么是执行之间的区别可比和比较？

有关完整性，我要告诫大家，回报o1.f - o2.f 比较逐减快捷方式必须慎用由于可能溢出（读有效的Java第二版：第12项：考虑实施可比 的）。 presumably曲棍球不是一个的运动，一名球员能够进球的金额，将导致问题=）

For completeness, I should caution that the return o1.f - o2.f comparison-by-subtraction shortcut must be used with extreme caution due to possible overflows (read: Effective Java 2nd Edition: Item 12: Consider implementing Comparable). Presumably hockey isn't a sport where a player can score goals in the amount that would cause problems =)

• Java整型：什么是比较快或减法

• Java Integer: what is faster comparison or subtraction?

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