大陆各运营商IP段统计

2.11、考虑一种关系（重点）

现在要求通过该类表示出如下的关系：

• 一个人有一本书，一本书属于一个人

按照类的划分，本句话可以划分出两个操作类：Person、Book

class Person {
    private String name;
    private int age;
    private Book book; //一个人有一本书
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public void setBook(Book book) {
        this.book = book;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
    public Book getBook() {
        return book;
    }
}
class Book {
    private String title;
    private float price;
    private Person person;
    public Book(String title, float price) {
        this.title = title;
        this.price = price;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    public void setPerson(Person person) {
        this.person = person;
    }
    public String getTitle() {
        return title;
    }
    public float getPrice() {
        return price;
    }
    public Person getPerson() {
        return person;
    }
}

public class Demo02 {
    public static void main(String args[]) {
        Person per = new Person("张三", 30);
        Book bk = new Book("java基础", 89.0f);
        per.setBook(bk);        //一个人有一本书
        bk.setPerson(per);      //一本书属于一个人
        System.out.println(per.getBook().getTitle());   //有人找到其所拥有书的名字
        System.out.println(bk.getPerson().getName());      //由书找到人的名字
    }
};

进一步延伸

• 一个人不光有一本书，还可能有一个孩子，那么此种关系又该如何表示呢？

class Person {
    private String name;
    private int age;
    private Book book; //一个人有一本书
    private Person child;
    public Person getChild() {
        return child;
    }
    public void setChild(Person child) {
        this.child = child;
    }
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public void setBook(Book book) {
        this.book = book;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
    public Book getBook() {
        return book;
    }
}
class Book {
    private String title;
    private float price;
    private Person person;
    public Book(String title, float price) {
        this.title = title;
        this.price = price;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    public void setPerson(Person person) {
        this.person = person;
    }
    public String getTitle() {
        return title;
    }
    public float getPrice() {
        return price;
    }
    public Person getPerson() {
        return person;
    }
}

public class Demo02 {
    public static void main(String args[]) {
        Person per = new Person("张三", 30);
        Person cld = new Person("李四", 10);
        Book bk = new Book("java基础", 89.0f);
        Book bkc = new Book("童话故事", 89.0f);
        per.setBook(bk);        //一个人有一本书
        cld.setBook(bkc);
        bk.setPerson(per);      //一本书属于一个人
        bkc.setPerson(cld);
        System.out.println(per.getBook().getTitle());   //有人找到其所拥有书的名字
        System.out.println(bk.getPerson().getName());      //由书找到人的名字
        System.out.println(cld.getBook().getTitle());
        System.out.println(bkc.getPerson().getName());
    }
};

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