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GoF23 原型模式学习笔记

原型模式（Prototype Pattern）是一种软件设计模式，允许你通过复制现有的对象来创建新对象，而不必重新编写代码。这个模式特别适用于需要多次创建对象的情况，能够有效减少代码冗余。

实现Cloneable接口与重写clone方法

在Java中，实现Cloneable接口并重写clone方法是使用原型模式的关键步骤。通过这种方式，类可以定义自己的复制机制，而不是直接继承自Object类的clone方法。

应用场景

浅拷贝与深拷贝的区别

在原型模式中，复制对象的方式分为浅拷贝和深拷贝两种：

代码示例

浅拷贝实现

package prototype.shallow;import java.util.Date;public class Video implements Cloneable {    private String name;    private Date publishTime;    public Video(String name, Date publishTime) {        this.name = name;        this.publishTime = publishTime;    }    public Video() {}    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Date getPublishTime() {        return publishTime;    }    public void setPublishTime(Date publishTime) {        this.publishTime = publishTime;    }    @Override    protected Object clone() throws CloneNotSupportedException {        return super.clone();    }    @Override    public String toString() {        return "Video [name=" + name + ", publishTime=" + publishTime + "]";    }}

浅拷贝测试

package prototype.shallow;import java.util.Date;public class Main {    public static void main(String[] args) throws CloneNotSupportedException {        Date date = new Date();        Video video = new Video("VideoName", date);        Video cloneVideo = (Video) video.clone();        System.out.println(video); // 输出: Video [name=VideoName, publishTime=当前时间]        System.out.println(cloneVideo); // 输出: Video [name=VideoName, publishTime=当前时间]        date.setTime(1231241);        System.out.println(video); // 输出: Video [name=VideoName, publishTime=修改后的时间]        System.out.println(cloneVideo); // 输出: Video [name=VideoName, publishTime=修改后的时间]    }}

深拷贝实现

package prototype.deep;import java.util.Date;public class Video implements Cloneable {    private String name;    private Date publishTime;    public Video(String name, Date publishTime) {        this.name = name;        this.publishTime = publishTime;    }    public Video() {}    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Date getPublishTime() {        return publishTime;    }    public void setPublishTime(Date publishTime) {        this.publishTime = publishTime;    }    @Override    protected Object clone() throws CloneNotSupportedException {        Object obj = super.clone();        Video v = (Video) obj;        v.publishTime = (Date) this.publishTime.clone();        return obj;    }    @Override    public String toString() {        return "Video [name=" + name + ", publishTime=" + publishTime + "]";    }}

深拷贝测试

package prototype.deep;import java.util.Date;public class Main {    public static void main(String[] args) throws CloneNotSupportedException {        Date date = new Date();        Video video = new Video("VideoName", date);        Video cloneVideo = (Video) video.clone();        System.out.println(video); // 输出: Video [name=VideoName, publishTime=当前时间]        System.out.println(cloneVideo); // 输出: Video [name=VideoName, publishTime=当前时间]        date.setTime(1231241);        System.out.println(video); // 输出: Video [name=VideoName, publishTime=修改后的时间]        System.out.println(cloneVideo); // 输出: Video [name=VideoName, publishTime=修改后的时间]    }}

总结

通过实现 Cloneable 接口并重写 clone 方法，你可以在代码中轻松实现对象的复制。浅拷贝和深拷贝的区别在于，浅拷贝只复制对象的引用，而深拷贝复制对象的所有属性，包括对象的引用属性。在实际开发中，选择使用浅拷贝还是深拷贝取决于对象的复杂度和设计需求。

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