如何通过属性对对象的数组列表排序？ [英] How to sort an arraylist of objects by a property?

问题描述

假设您有 Arraylist 的 HockeyPlayer 对象。

如果他们都有一个变量 int goalsScored ，如何排序呢？

解决方案

您可以使用 Collections.sort 与自定义 Comparator< HockeyPlayer> 。

  class HockeyPlayer {
 public final int goalsScored; 
 // ... 
}; 
 
 List< HockeyPlayer> players = // ... 
 
 Collections.sort（players，new Comparator< HockeyPlayer>（）{
 @Override public int compare（HockeyPlayer p1，HockeyPlayer p2）{
 return p1.goalsScored  -  p2.goalsScored; // Ascending 
} 
 
}）;或者，您可以使 HockeyPlayer implements     a href =http://java.sun.com/javase/6/docs/api/java/lang/Comparable.html =nofollow noreferrer> 可比较的< HockeyPlayer>  。这为所有 HockeyPlayer 对象定义自然顺序。使用比较器更灵活，因为不同的实现可以按名称，年龄等进行排序。
 
 
 
 / h3> 
 
 
 
 
  Java：实现 Comparable 和 Comparator 之间有什么区别？ 
 
 
 
 
 
 
 
 
为了完整起见，我应该注意 return由于可能的溢出，必须非常小心使用比较减法快捷方式（读取： Effective Java第2版：项目12：考虑实现 Comparable  ）。推测曲棍球不是一种运动，其中玩家可以导致问题的数量的目标）=）
 
 
 
参见
 
 
 
 
 
  Java整数：什么是更快的比较或减法？ 
 
 
 
Lets say you have an Arraylist of HockeyPlayer objects.  

How could you sort that if they all have a variable int goalsScored.  How could you sort them by goalsScored?
解决方案
You can use Collections.sort with a custom Comparator<HockeyPlayer>.
    class HockeyPlayer {
        public final int goalsScored;
        // ...
    };

    List<HockeyPlayer> players = // ...

    Collections.sort(players, new Comparator<HockeyPlayer>() {
        @Override public int compare(HockeyPlayer p1, HockeyPlayer p2) {
            return p1.goalsScored - p2.goalsScored; // Ascending
        }

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

See also


Java: What is the difference between implementing Comparable and Comparator?




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 =)

See also


Java Integer: what is faster comparison or subtraction?


                        
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