java設計模式-克隆模式（複製模式）

java中有深克隆和淺克隆的說法，clone方法在Object類中，該方法被protect修飾，我們無法直接調用，只能實現Cloneable接口，重寫clone方法，我們舉個作家和書本的栗子說明

首先解釋深克隆，創建作家類

public class Person implements Cloneable{

    private String name;
    private String gender;
    private int age;

    public Person(String name, String gender, int age) {
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
    public void display(){
        System.out.println("姓名："+this.name+"性別："+this.gender+"年齡："+this.age);
    }

    public Object clone(){
        Person p = null;
        try {
            p = (Person)super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return p;
    }

    @Override
    public String toString() {
        return "name=" + name + ", gender=" + gender + ", age=" + age ;
    }
}

然後創建書籍類

ublic class BookForDeep implements Cloneable {

    private String bookName;
    private double price;
    private Person author;

    public BookForDeep(String bookName, double price, Person author) {
        this.bookName = bookName;
        this.price = price;
        this.author = author;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public Person getAuthor() {
        return author;
    }

    public void setAuthor(Person author) {
        this.author = author;
    }

    public void display() {
        System.out.println("書名：" + bookName + " 價格： " + price + "作者：" + author);
    }

    public String toString() {
        return "bookName: " + bookName + "price: " + price + "author:" + author;
    }

    public Object clone() throws CloneNotSupportedException {
        BookForDeep bfp = null;
        bfp = (BookForDeep) super.clone();
        bfp.setAuthor((Person) super.clone());
        return bfp;
    }
}

我們寫一個測試類

public class TestBookForDeepClone {

    public static void main(String[] args) {
        BookForDeep bfd1 = new BookForDeep("Hadoop權威指南", 0.01, new Person("xiaoli", "female", 23));
        BookForDeep bfd2 = new BookForDeep("spark高級詳解", 0.01, new Person("azhong", "male", 24));

        System.out.println(bfd1.getAuthor() == bfd2.getAuthor());
        bfd1.display();
        bfd2.display();
    }
}

測試結果

false
書名： Hadoop權威指南 價格： 0.01作者：name=xiaoli, gender=female, age=23
姓名：xiaoli性別：female年齡：23
書名： spark高級詳解 價格： 0.01作者：name=azhong, gender=male, age=24
姓名：azhong性別：male年齡：24

我們再類測試淺克隆
創建BookForDeep類實現Cloneable在這裏我們需要修改clone方法，其他地方一樣

public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

寫一個測試類，測試淺克隆

public class TestBookLowClone {

    public static void main(String[] args) throws CloneNotSupportedException {
        Book book1 = new Book("Hadoop權威指南", 0.1, new Person("阿中", "male", 24));
        Book book2 = (Book) book1.clone();

        System.out.println(book1.getAuthor());
        System.out.println(book2.getAuthor());
        System.out.println(book1.getAuthor() == book2.getAuthor());
        book1.display();
        book2.display();
// 淺拷貝的問題：當更新副本中屬性指向的對象內容時 原對象的屬性會跟着一起變化
        // 因爲原對象中屬性的對象與副本中屬性的對象是同一個對象
        book2.getAuthor().setName("Allen");
        book2.getAuthor().setGender("female");
        book1.display();
        book2.display();
    }
}

運行結果

name=阿中, gender=male, age=24
name=阿中, gender=male, age=24
true
書名： Hadoop權威指南價格： 0.1作者：name=阿中, gender=male, age=24
姓名：阿中性別：male年齡：24
書名： Hadoop權威指南價格： 0.1作者：name=阿中, gender=male, age=24
姓名：阿中性別：male年齡：24
書名： Hadoop權威指南價格： 0.1作者：name=Allen, gender=female, age=24
姓名：Allen性別：female年齡：24
書名： Hadoop權威指南價格： 0.1作者：name=Allen, gender=female, age=24
姓名：Allen性別：female年齡：24