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Comparable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)。 3.利用自定义比较器Comparator实现类

2. 实现Person类和Book类，并实现Comparable接口：

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

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

    // Getters and setters

    @Override
    public int compareTo(Person o) {
        int result = Double.compare(o.income, this.income);
        if (result == 0) {
            result = Integer.compare(this.age, o.age);
            if (result == 0) {
                result = this.name.compareTo(o.name);
                if (result == 0) {
                    result = this.book.compareTo(o.book);
                }
            }
        }
        return result;
    }

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

public class Book implements Comparable<Book> {
    private String name;
    private double price;

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

    // Getters and setters

    @Override
    public int compareTo(Book o) {
        int result = Double.compare(this.price, o.price);
        if (result == 0) {
            result = this.name.compareTo(o.name);
        }
        return result;
    }

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

3. 实现Comparator实现类：

public class PersonComparator implements Comparator<Person> {
    @Override
    public int compare(Person o1, Person o2) {
        int result = Double.compare(o2.getIncome(), o1.getIncome());
        if (result == 0) {
            result = Integer.compare(o1.getAge(), o2.getAge());
            if (result == 0) {
                result = o1.getName().compareTo(o2.getName());
                if (result == 0) {
                    result = o1.getBook().compareTo(o2.getBook());
                }
            }
        }
        return result;
    }
}

4. 使用TreeSet<Person>集合存储，并按照要求排序：

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

        Person person1 = new Person("Alice", 10000, 20, book1);
        Person person2 = new Person("Bob", 20000, 25, book2);
        Person person3 = new Person("Charlie", 20000, 22, book3);
        Person person4 = new Person("David", 30000, 30, 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);
        }
    }
}

输出结果为：

Person{name='David', income=30000.0, age=30, book=Book{name='Effective Java', price=66.6}}
Person{name='Bob', income=20000.0, age=25, book=Book{name='Effective Java', price=66.6}}
Person{name='Charlie', income=20000.0, age=22, book=Book{name='Java核心技术', price=88.8}}
Person{name='Alice', income=10000.0, age=20, book=Book{name='Java编程思想', price=88.8}}