如何按属性对对象数组列表进行排序? [英] How to sort an arraylist of objects by a property?

问题描述

假设您有一个 HockeyPlayer 对象的 Arraylist.

Lets say you have an Arraylist of HockeyPlayer objects.

如果他们都有一个变量int目标得分，你怎么排序.您如何按目标得分对它们进行排序?

How could you sort that if they all have a variable int goalsScored. How could you sort them by goalsScored?

推荐答案

您可以使用 Collections.sort 带有自定义 Comparator.

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
        }

    });

比较部分也可以这样写:

The comparision part can also be written this way :

players.sort(Comparator.comparingInt(HockeyPLayer::goalsScored));

或者，您可以使 HockeyPlayer 实现可比的.这定义了所有 HockeyPlayer 对象的 自然顺序.使用 Comparator 更加灵活，因为不同的实现可以按名称、年龄等排序.

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.

• Java:实现Comparable 和 Comparator?

为了完整起见，我应该注意 return o1.f - o2.f 比较减法快捷方式必须非常谨慎，因为可能会溢出(阅读:Effective Java第二版:第 12 项:考虑实现 Comparable).大概曲棍球不是一项运动，其中球员可以进球的数量会导致问题=)

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 整数:什么是更快的比较或减法?

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