按多个字段对对象列表排序 [英] Sort a List of objects by multiple fields

问题描述

我有一个Java对象列表，我想根据多个字段排序。

I have a List of Java objects that I want to sort according to more than one field.

public class graduationCeremony {
    String campus;
    String faculty;
    String building;
}

是否可以使用 Comparator 或 Comparable 接口根据多个字段对列表排序？我看到的所有例子只根据一个字段排序。换句话说，人们可以通过校园或教师或建筑来排序。我想按照校园，然后是教师，然后是建筑来排序（如在SQL中存在： ORDER BY campus，faculty，building ）

Is it possible to use a Comparator or the Comparable interface to sort the list according to multiple fields? All the examples I have seen sort according to only one field. In other words, one can sort by 'campus' OR 'faculty' OR 'building'. I want to sort by 'campus', then 'faculty', then 'building' (as it exists in SQL: ORDER BY campus, faculty, building)

我认为这个问题已经问前，但我不明白接受的答案。

I think this question has been asked before, but I don't understand the accepted answer. Can someone expand or illustrate this answer?

推荐答案

您的比较器将如下所示：

Your Comparator would look like this:

public class GraduationCeremonyComparator implements Comparator<graduationCeremony> {
    public int compare(graduationCeremony o1, graduationCeremony o2) {
        int value1 = o1.campus.compareTo(o2.campus);
        if (value1 == 0) {
            int value2 = o1.faculty.compareTo(o2.faculty);
            if (value2 == 0) {
                return o1.building.compareTo(o2.building);
            } else {
                return value2;
        }
        return value1;
    }
}

基本上它会继续比较你的类的每个连续属性到目前为止，比较的属性是相等的（ == 0 ）。

Basically it continues comparing each successive attribute of your class whenever the compared attributes so far are equal (== 0).

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