设计模式--原型模式--- prototype

参考：https://blog.csdn.net/weixin_48052161/article/details/119493380
原型模式
定义;
原型模式属于对象创建模式，GOF 给它的定义为：用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。
Java中的原型模式:
在 Java 中提供了clone()方法来实现对象的克隆，所以Prototype 模式实现变得简单许 多。

原型模式分为

浅克隆
深克隆

代码演示：

浅克隆：
实现条件:
1. implements Cloneable接口
2. 重写clone()方法

location类（person内部的调用类）：

package com.example.dtest.design23.prototype;

public class Location {

    String street;
    int roomNo;

    @Override
    public String toString() {
        return "Location{" +
                "street='" + street + ''' +
                ", roomNo=" + roomNo +
                '}';
    }

    public Location(String street,int roomNo){
        this.street = street;
        this.roomNo = roomNo;
    }

}

person类：

package com.example.dtest.design23.prototype;

public class Person implements Cloneable {

    int age = 8;
    int score = 100;
    Location loc = new Location("北京", 22);

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

}

测试类：

package com.example.dtest.design23.prototype;

public class Location {

    String street;
    int roomNo;

    @Override
    public String toString() {
        return "Location{" +
                "street='" + street + ''' +
                ", roomNo=" + roomNo +
                '}';
    }

    public Location(String street,int roomNo){
        this.street = street;
        this.roomNo = roomNo;
    }

}

可以看出 p2是有p1克隆过去的,且p1和p2.地址值不同,但成员属性相同
p1和p2的成员属性loc相同,都是指向堆中同一地址.即 p1.loc==p2.loc为true
所以当p1改变属性loc时,p2的属性loc也随之改变,这就是浅克隆

如果想克隆出来的p2不随p1改变而改变 ,则需要进行深克隆

深克隆：
location也继承了cloneable类：

package com.example.dtest.design23.prototype.deepPrototype;

public class Location implements Cloneable{

    String street;
    int roomNo;

    public Location(String street,int roomNo){
        this.street = street;
        this.roomNo = roomNo;
    }


    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    @Override
    public String toString() {
        return "Location{" +
                "street='" + street + ''' +
                ", roomNo=" + roomNo +
                '}';
    }
}

person类：

package com.example.dtest.design23.prototype.deepPrototype;

public class Person implements Cloneable{

    int age = 8;
    int score = 100;

    Location loc = new Location("北京", 22);

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Person p = (Person) super.clone();
        p.loc = (Location) loc.clone();
        return p;
    }

}

测试类：

package com.example.dtest.design23.prototype.deepPrototype;

public class DeepPrototypeTest {

    public static void main(String[] args) {
        Person p1 = new Person();
        Person p2;
        try {
             p2 = (Person) p1.clone();
            System.out.println(p2.age + "" + p2.score);
            System.out.println(p2.loc);
            System.out.println("--------------------");

            System.out.println("p1==p2: "+(p1 == p2));
            System.out.println("p1.loc==p2.loc: "+(p1.loc == p2.loc));

            p1.loc.street = "上海";
            System.out.println("p1.loc:  "+p1.loc);
            System.out.println("p2.loc:  "+p2.loc);

        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }

    }

}

分析: 可以看出p1改变自己的属性loc 时,p2并不会随之变化