java lambda分组后再排序

可以使用Java 8中的Stream API和lambda表达式来实现分组后排序的功能。下面是一个示例代码：

import java.util.*;
import java.util.stream.Collectors;

public class GroupingAndSortingExample {
    public static void main(String[] args) {
        // 创建一个学生列表
        List<Student> students = Arrays.asList(
                new Student("Tom", 18, 80),
                new Student("Jerry", 17, 90),
                new Student("Lucy", 18, 95),
                new Student("Bob", 17, 85),
                new Student("Alice", 18, 92)
        );

        // 按年龄分组，并按分数排序
        Map<Integer, List<Student>> map = students.stream()
                .collect(Collectors.groupingBy(Student::getAge,
                        Collectors.collectingAndThen(Collectors.toList(),
                                list -> list.stream()
                                        .sorted(Comparator.comparing(Student::getScore))
                                        .collect(Collectors.toList()))));

        // 打印结果
        map.forEach((age, list) -> {
            System.out.println("Age: " + age);
            list.forEach(System.out::println);
        });
    }
}

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

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public int getScore() {
        return score;
    }

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

以上代码将学生列表按年龄分组，并按照分数进行排序。可以根据需要修改Student类的字段和排序方式。