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 实现类完成第 2 题。

Person 类定义如下：

import java.util.*;

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;
    }

    public String getName() {
        return name;
    }

    public double 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 -1;
        } else if (this.income < other.income) {
            return 1;
        } else {
            if (this.age < other.age) {
                return -1;
            } else if (this.age > other.age) {
                return 1;
            } else {
                int nameCompare = this.name.compareTo(other.name);
                if (nameCompare != 0) {
                    return nameCompare;
                } else {
                    if (this.book.getPrice() < other.book.getPrice()) {
                        return -1;
                    } else if (this.book.getPrice() > other.book.getPrice()) {
                        return 1;
                    } else {
                        return this.book.getName().compareTo(other.book.getName());
                    }
                }
            }
        }
    }
}

Book 类定义如下：

public 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;
    }
}

使用 TreeSet<Person> 集合存储，并按照要求排序的示例代码如下：

public class PersonComparator implements Comparator<Person> {
    @Override
    public int compare(Person p1, Person p2) {
        if (p1.getIncome() > p2.getIncome()) {
            return -1;
        } else if (p1.getIncome() < p2.getIncome()) {
            return 1;
        } else {
            if (p1.getAge() < p2.getAge()) {
                return -1;
            } else if (p1.getAge() > p2.getAge()) {
                return 1;
            } else {
                int nameCompare = p1.getName().compareTo(p2.getName());
                if (nameCompare != 0) {
                    return nameCompare;
                } else {
                    if (p1.getBook().getPrice() < p2.getBook().getPrice()) {
                        return -1;
                    } else if (p1.getBook().getPrice() > p2.getBook().getPrice()) {
                        return 1;
                    } else {
                        return p1.getBook().getName().compareTo(p2.getBook().getName());
                    }
                }
            }
        }
    }

    public static void main(String[] args) {
        Book b1 = new Book("Java Programming", 45.0);
        Book b2 = new Book("Data Structures", 60.0);
        Book b3 = new Book("Algorithm Design", 45.0);

        Person p1 = new Person("Alice", 100000, 25, b1);
        Person p2 = new Person("Bob", 80000, 30, b2);
        Person p3 = new Person("Charlie", 100000, 25, b3);

        TreeSet<Person> people = new TreeSet<>(new PersonComparator());
        people.add(p1);
        people.add(p2);
        people.add(p3);

        for (Person p : people) {
            System.out.println(p.getName() + " " + p.getIncome() + " " + p.getAge() + " " + p.getBook().getName() + " " + p.getBook().getPrice());
        }
    }
}

输出结果如下：

Charlie 100000.0 25 Algorithm Design 45.0
Alice 100000.0 25 Java Programming 45.0
Bob 80000.0 30 Data Structures 60.0