定义一个 Person 类。 属性有: 姓名、 收入、 年龄、 书(一本)。 定义一个 Book 类; 属性有: 书名、 价格。 要求用 Comparable 接口实现, 使用 TreeSet<Person>集合存储, 排序规则:

根据收入从高到低排序，如果收入相同则按照年龄从小到大排序。

以下是示例代码：

import java.util.*;

class Person implements Comparable<Person> {
    private String name;
    private int income;
    private int age;
    private Book book;

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

    public String getName() {
        return name;
    }

    public int getIncome() {
        return income;
    }

    public int getAge() {
        return age;
    }

    public Book getBook() {
        return book;
    }

    @Override
    public int compareTo(Person other) {
        if (this.income != other.income) {
            return other.income - this.income;
        } else {
            return this.age - other.age;
        }
    }

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

class Book {
    private String name;
    private double price;

    public Book(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }

    public double getPrice() {
        return price;
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", price=" + price +
                '}';
    }
}

public class Main {
    public static void main(String[] args) {
        Book book1 = new Book("Java编程思想", 99.9);
        Book book2 = new Book("Java核心技术", 88.8);
        Book book3 = new Book("Effective Java", 66.6);

        Person person1 = new Person("Tom", 100000, 30, book1);
        Person person2 = new Person("Jerry", 80000, 25, book2);
        Person person3 = new Person("Bob", 90000, 35, book3);

        TreeSet<Person> set = new TreeSet<>();
        set.add(person1);
        set.add(person2);
        set.add(person3);

        for (Person person : set) {
            System.out.println(person);
        }
    }
}

输出结果为:

Person{name='Tom', income=100000, age=30, book=Book{name='Java编程思想', price=99.9}}
Person{name='Bob', income=90000, age=35, book=Book{name='Effective Java', price=66.6}}
Person{name='Jerry', income=80000, age=25, book=Book{name='Java核心技术', price=88.8}}