使用Lambdas将List<Person>转换为Map<Integer和List<Integer>>

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

public class Main {
    public static void main(String[] args) {
        // 示例数据
        List<Person> personList = Arrays.asList(
                new Person("Alice", 25),
                new Person("Bob", 30),
                new Person("Charlie", 25),
                new Person("Dave", 30)
        );

        // 使用Lambdas将List<Person>转换为Map<Integer, List<Integer>>
        Map<Integer, List<String>> ageToNamesMap = personList.stream()
                .collect(Collectors.groupingBy(Person::getAge, Collectors.mapping(Person::getName, Collectors.toList())));

        // 打印转换结果
        ageToNamesMap.forEach((age, names) -> System.out.println("Age: " + age + ", Names: " + names));
    }

    static 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;
        }
    }
}