如何使用Java Lambda表达式实现Java流式处理中的动态分组？

import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

class Student {
    String name;
    String sex;
    int age;

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

    public String getSex() { return sex; }
    public Integer getAge() { return age; }
    @Override
    public String toString() { return name + "(" + sex + "," + age + ")"; }
}

public class DynamicGrouping {

    public static <T, K> List<T> groupBy(List<T> list, Function<T, K> classifier) {
        Map<K, List<T>> grouped = list.stream().collect(Collectors.groupingBy(classifier));
        return grouped.values().stream().flatMap(Collection::stream).collect(Collectors.toList());
    }

    public static void main(String[] args) {
        List<Student> students = Arrays.asList(
                new Student("Alice", "female", 20),
                new Student("Bob", "male", 22),
                new Student("Charlie", "male", 23),
                new Student("Alice", "female", 21),
                new Student("Bob", "male", 22)
        );

        List<Student> groupedBySex = groupBy(students, Student::getSex);
        List<Student> groupedByAge = groupBy(students, Student::getAge);

        System.out.println("Grouped by Sex: " + groupedBySex);
        System.out.println("Grouped by Age: " + groupedByAge);
    }
}