Java在GroupBy之后排序

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        // 假设有一个包含学生信息的列表
        List<Student> students = Arrays.asList(
                new Student("Alice", "Math", 80),
                new Student("Bob", "Math", 90),
                new Student("Alice", "English", 85),
                new Student("Bob", "English", 95),
                new Student("Alice", "Science", 75),
                new Student("Bob", "Science", 85)
        );

        // 使用GroupBy按照学生姓名进行分组
        Map<String, List<Student>> groupedStudents = students.stream()
                .collect(Collectors.groupingBy(Student::getName));

        // 对每个分组内的学生按照成绩进行排序
        groupedStudents.forEach((name, group) -> {
            List<Student> sortedGroup = group.stream()
                    .sorted((s1, s2) -> s2.getScore() - s1.getScore())
                    .collect(Collectors.toList());

            System.out.println("Group: " + name);
            sortedGroup.forEach(System.out::println);
            System.out.println();
        });
    }
}

class Student {
    private String name;
    private String subject;
    private int score;

    public Student(String name, String subject, int score) {
        this.name = name;
        this.subject = subject;
        this.score = score;
    }

    public String getName() {
        return name;
    }

    public String getSubject() {
        return subject;
    }

    public int getScore() {
        return score;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", subject='" + subject + '\'' +
                ", score=" + score +
                '}';
    }
}