从 HashMap 中选取 Top N 个最高值对应的键，并转换为列表

import java.util.*;

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 TopNKeys {

    public static List<Person> getTopNKeys(Map<Person, Integer> map, int n) {
        // 1. 将 Map 转换为 List<Map.Entry<Person, Integer>>
        List<Map.Entry<Person, Integer>> entries = new ArrayList<>(map.entrySet());

        // 2. 使用 Collections.sort 和 Comparator 对 List 进行排序（按值降序）
        Collections.sort(entries, Comparator.comparing(Map.Entry::getValue, (v1, v2) -> v2.compareTo(v1)));

        // 3. 提取 Top N 个键
        List<Person> topNKeys = new ArrayList<>();
        for (int i = 0; i < Math.min(n, entries.size()); i++) {
            topNKeys.add(entries.get(i).getKey());
        }

        return topNKeys;
    }

    public static void main(String[] args) {
        Map<Person, Integer> personMap = new HashMap<>();
        personMap.put(new Person("Alice", 30), 100);
        personMap.put(new Person("Bob", 25), 80);
        personMap.put(new Person("Charlie", 35), 120);
        personMap.put(new Person("David", 28), 90);
        personMap.put(new Person("Eve", 22), 110);

        int n = 3;
        List<Person> topN = getTopNKeys(personMap, n);

        System.out.println("Top " + n + " Persons with highest values:");
        for (Person person : topN) {
            System.out.println(person);
        }
    }
}