2. 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 Comparator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, 字典顺序(String 类的 compareTo 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)。

代码如下：

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

class 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 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 +
                '}';
    }
}

class PersonComparator implements Comparator<Person>{

    @Override
    public int compare(Person o1, Person o2) {
        if(o1.getIncome() != o2.getIncome()){
            return o2.getIncome() - o1.getIncome();
        }else if(o1.getAge() != o2.getAge()){
            return o1.getAge() - o2.getAge();
        }else if(!o1.getName().equals(o2.getName())){
            return o1.getName().compareTo(o2.getName());
        }else{
            if(o1.getBook().getPrice() != o2.getBook().getPrice()){
                return (int)(o1.getBook().getPrice() - o2.getBook().getPrice());
            }else{
                return o1.getBook().getName().compareTo(o2.getBook().getName());
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        Book book1 = new Book("Java", 59.9);
        Book book2 = new Book("Python", 49.9);
        Book book3 = new Book("C++", 29.9);

        Person person1 = new Person("Tom", 5000, 23, book1);
        Person person2 = new Person("Jerry", 6000, 25, book2);
        Person person3 = new Person("Alice", 6000, 23, book3);
        Person person4 = new Person("Bob", 7000, 22, book2);

        TreeSet<Person> set = new TreeSet<>(new PersonComparator());
        set.add(person1);
        set.add(person2);
        set.add(person3);
        set.add(person4);

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

输出结果：

Person{name='Bob', income=7000, age=22, book=Book{name='Python', price=49.9}}
Person{name='Jerry', income=6000, age=25, book=Book{name='Python', price=49.9}}
Person{name='Alice', income=6000, age=23, book=Book{name='C++', price=29.9}}
Person{name='Tom', income=5000, age=23, book=Book{name='Java', price=59.9}}