如何使用groupingBy收集器创建对象列表而不是映射？

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

class Person {
    private String name;
    private int age;

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

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

public class GroupingByExample {
    public static void main(String[] args) {
        List<Person> people = Arrays.asList(
            new Person("Alice", 25),
            new Person("Bob", 30),
            new Person("Charlie", 25),
            new Person("David", 30)
        );

        // 使用 groupingBy 收集器按年龄分组
        Map<Integer, List<Person>> peopleByAge = people.stream()
            .collect(Collectors.groupingBy(Person::getAge));

        // 将分组结果转换为对象列表
        List<List<Person>> groupedPeopleList = new ArrayList<>(peopleByAge.values());

        // 打印结果
        groupedPeopleList.forEach(group -> {
            System.out.println("Age group: " + group.get(0).getAge());
            group.forEach(System.out::println);
            System.out.println();
        });
    }
}

Age group: 25
Person{name='Alice', age=25}
Person{name='Charlie', age=25}

Age group: 30
Person{name='Bob', age=30}
Person{name='David', age=30}