Java - 如何用季节和年份对字符串的 ArrayList 进行排序？

Question

我有一个未排序的 ArrayList 的季节和年份字符串，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命令？ 一年中的季节顺序是 2021 年冬季、2021 年春季、2021 年夏季、2021 年秋季，并且列表中不一定存在每年的所有季节。

Answer 1

您需要实现一个自定义Comparator ，首先按年份排序，然后按季节排序。 enum可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]

Answer 2

您需要为此类字符串编写自己的comparator 。 我建议你使用arrow函数。 另外，要对季节进行排序，您需要给它们一些优先级，我会使用Map<String, Integer>来表示它。

试试这个代码：

public static void main(String[] args) {
    Map<String, Integer> seasonsPriority = new HashMap<>();
    seasonsPriority.put("Winter", 1);
    seasonsPriority.put("Spring", 2);
    seasonsPriority.put("Summer", 3);
    seasonsPriority.put("Autumn", 4);

    ArrayList<String> seasons = new ArrayList<>();
    seasons.add("Summer 2020");
    seasons.add("Autumn 2018");
    seasons.add("Spring 2019");
    seasons.add("Autumn 2019");
    seasons.add("Winter 2018");
    seasons.add("Summer 2018");
    seasons.add("Winter 2020");
    seasons.add("Spring 2018");


    seasons.sort((x, y) -> {
        int firstYear = Integer.parseInt(x.split(" ")[1]);
        int secondYear = Integer.parseInt(y.split(" ")[1]);

        if(firstYear < secondYear) {
            return -1;
        }

        if(firstYear > secondYear) {
            return 1;
        }

        String firstSeason = x.split(" ")[0];
        String secondSeason = y.split(" ")[0];

        return Integer.compare(seasonsPriority.get(firstSeason), seasonsPriority.get(secondSeason));
    });

    System.out.println(seasons);
}

输出：

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

Answer 3

考虑编写自定义 Comparator 以使用自定义逻辑执行排序。

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

    List<String> listOfSeasonsInAscendingOrder = Arrays.asList("Winter", "Spring", "Summer", "Autumn");

    Collections.sort(list, new Comparator<String>() {
        @Override
        public int compare(String o1, String o2) {
            String firstStringSplit[] = o1.split(" ");
            String season1 = firstStringSplit[0];
            int year1 = Integer.valueOf(firstStringSplit[1]);

            String secondStringSplit[] = o2.split(" ");
            String season2 = secondStringSplit[0];
            int year2 = Integer.valueOf(secondStringSplit[1]);

            if (year1 != year2) {
                return year1 < year2 ? -1 : 1;
            }

            int indexOfSeason1 = listOfSeasonsInAscendingOrder.indexOf(season1);
            int indexOfSeason2 = listOfSeasonsInAscendingOrder.indexOf(season2);

            return indexOfSeason1 == indexOfSeason2 ? 0 : indexOfSeason1 < indexOfSeason2 ? -1 : 1;
        }
    });

    System.out.println("Sorted List = " + list);
}

上面代码的输出是：-

Sorted List = [Winter 2018, Spring 2018, Summer 2018, Autumn 2018, Spring 2019, Autumn 2019, Winter 2020, Summer 2020]

Answer 4

试试这个。

static final Map<String, Integer> SEASON_ORDER = Map.of(
    "Winter", 0, "Spring", 1, "Summer", 2, "Autumn", 3);

public static void main(String[] args) {
    List<String> list = new ArrayList<>(List.of(
        "Summer 2020", "Autumn 2018", "Spring 2019", "Autumn 2019",
        "Winter 2018", "Summer 2018", "Winter 2020", "Spring 2018"));
    list.sort(Comparator.comparing(s -> {
        String[] a = s.split("\\s+");
        return a[1] + SEASON_ORDER.get(a[0]);
    }));
    System.out.println(list);
}

输出：

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