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 Gomparable 接口实现，使用TreeSet<Person>集合 存储，排序规则： A.先按照收入从高到低排序； B.收入相等的情况下，按照年龄从小到大排序； C. 如果收入和年龄都相等，按照姓名排序，宇典顺序(String 类的cormpareTo方法）； D.如果以上3个属性都相等，按照书排序，先按照书价格从低到高，如果书价格相等，按照书名(字典顺序）。

下面是代码实现：

import java.util.Comparator;
import java.util.TreeSet;

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

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    public double getIncome() {
        return income;
    }

    public Book getBook() {
        return book;
    }

    @Override
    public int compareTo(Person o) {
        if (this.income != o.income) {
            return Double.compare(o.income, this.income);
        } else if (this.age != o.age) {
            return Integer.compare(this.age, o.age);
        } else if (!this.name.equals(o.name)) {
            return this.name.compareTo(o.name);
        } else {
            return this.book.compareTo(o.book);
        }
    }

    public static void main(String[] args) {
        Book book1 = new Book("Java基础", 50.0);
        Book book2 = new Book("Java高级", 60.0);
        Book book3 = new Book("数据结构", 40.0);
        Person person1 = new Person("Tom", 20, 10000, book1);
        Person person2 = new Person("Jerry", 25, 8000, book2);
        Person person3 = new Person("Mike", 30, 10000, book3);
        TreeSet<Person> set = new TreeSet<>();
        set.add(person1);
        set.add(person2);
        set.add(person3);
        for (Person p : set) {
            System.out.println(p.getName() + " " + p.getAge() + " " + p.getIncome() + " " + p.getBook().getName() + " " + p.getBook().getPrice());
        }
    }
}

class Book implements Comparable<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 int compareTo(Book o) {
        if (this.price != o.price) {
            return Double.compare(this.price, o.price);
        } else {
            return this.name.compareTo(o.name);
        }
    }
}

输出结果：

Tom 20 10000.0 Java高级 60.0
Mike 30 10000.0 数据结构 40.0
Jerry 25 8000.0 Java基础 50.0