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java - 如何按季节和年份对字符串的 ArrayList 进行排序？

问题描述

我有一个未排序的季节和年份字符串数组列表，如下所示：

["Summer 2020", "Autumn 2018", "Spring 2019", "Autumn 2019", "Winter 2018", "Summer 2018", "Winter 2020", "Spring 2018"]

此列表的正确排序如下：

["Winter 2018", "Spring 2018", "Summer 2018", "Autumn 2018", "Spring 2019", "Autumn 2019", "Winter 2020", "Summer 2020"]

我怎样才能实现这个订单？一年中的季节顺序为 2021 年冬季、2021 年春季、2021 年夏季、2021 年秋季，并且每年的所有季节都不一定存在于列表中。

标签： javalistsortingarraylist

解决方案

您需要实现一个自定义Comparator，先按年份排序，然后按季节排序。可enum用于轻松指定季节的顺序。

private static class SeasonComparator implements Comparator<String> {
    
    private enum Season {
        WINTER, SPRING, SUMMER, AUTUMN
    }

    @Override
    public int compare(String s1, String s2) {
        String[] arr1 = s1.split(" ");
        String[] arr2 = s2.split(" ");
        
        int year1 = Integer.parseInt(arr1[1]);
        int year2 = Integer.parseInt(arr2[1]);
        
        if (year1 != year2) {
            return year1 - year2;
        } else {
            Season season1 = Season.valueOf(arr1[0].toUpperCase());
            Season season2 = Season.valueOf(arr2[0].toUpperCase());
            return season1.ordinal() - season2.ordinal();
        }
    }
}

public static void main(String[] args) {
    List<String> seasons = new ArrayList<>(Arrays.asList("Summer 2020", "Autumn 2018",
            "Spring 2019", "Autumn 2019", "Winter 2018", "Summer 2018", "Winter 2020", "Spring 2018"));

    System.out.println("Unordered list:");
    System.out.println(seasons);
    
    seasons.sort(new SeasonComparator());
    
    System.out.println("Sorted list:");
    System.out.println(seasons);
}

输出

Unordered list:
[Summer 2020, Autumn 2018, Spring 2019, Autumn 2019, Winter 2018, Summer 2018, Winter 2020, Spring 2018]

Sorted list:
[Winter 2018, Spring 2018, Summer 2018, Autumn 2018, Spring 2019, Autumn 2019, Winter 2020, Summer 2020]

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