原型模式 | 易学教程

概念

定义：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
优缺点：
性能优良：原型模式是在内存二进制流的拷贝，比直接new一个对象性能要好很多
逃避构造函数的约束（既是优点也是缺点）
适用场景：
资源优化场景：类的初始化需要耗费非常多的资源的情况
性能和安全要求的场景：new一个对象需要繁琐的数据准备或者访问权限的情况
一个对象多个修改者的场景：一个对象需要提供给其他对象访问，而且各个调用者可能都需要修改其值时，可以拷贝多个对象供调用者使用，即保护性拷贝

代码实现

浅拷贝

@Data
class Attachment {
  private String name;
}

@Data
public class Mail implements Cloneable {
  private String receiver;
  private Attachment attachment;

  @Override
  protected Mail clone() {
    Mail cloneMail = null;
    try {
      cloneMail = (Mail) super.clone();
    } catch (CloneNotSupportedException e) {
      e.printStackTrace();
    }
    return cloneMail;
  }
}

public class Client {
  public static void main(String[] args) {
    Mail mail = new Mail();
    mail.setReceiver("Hua Lee");
    Attachment attachment = new Attachment();
    attachment.setName("new Attachment");
    mail.setAttachment(attachment);
    Mail cloneMail1 = mail.clone();
    cloneMail1.setReceiver("Feng Hu");
    cloneMail1.getAttachment().setName("new Attachment2");
    System.out.println(cloneMail1);
    Mail cloneMail2 = mail.clone();
    System.out.println(cloneMail2);
  }
}

在这里插入图片描述

深拷贝

@Data
class Attachment implements Cloneable {
  private String name;

  @Override
  protected Attachment clone() {
    Attachment cloneAttachment = null;
    try {
      cloneAttachment = (Attachment) super.clone();
    } catch (CloneNotSupportedException e) {
      e.printStackTrace();
    }
    return cloneAttachment;
  }
}

@Data
public class Mail implements Cloneable {
  private String receiver;
  private Attachment attachment;

  @Override
  protected Mail clone() {
    Mail cloneMail = null;
    try {
      cloneMail = (Mail) super.clone();
    } catch (CloneNotSupportedException e) {
      e.printStackTrace();
    }
    cloneMail.attachment = attachment.clone();
    return cloneMail;
  }
}

public class Client {
  public static void main(String[] args) {
    Mail mail = new Mail();
    mail.setReceiver("Hua Lee");
    Attachment attachment = new Attachment();
    attachment.setName("new Attachment");
    mail.setAttachment(attachment);
    Mail cloneMail1 = mail.clone();
    cloneMail1.setReceiver("Feng Hu");
    cloneMail1.getAttachment().setName("new Attachment2");
    System.out.println(cloneMail1);
    Mail cloneMail2 = mail.clone();
    System.out.println(cloneMail2);
  }
}

在这里插入图片描述

知识点

深拷贝和浅拷贝的区别：
深拷贝：对基本数据类型进行值传递，对引用数据类型只拷贝其内存地址
浅拷贝：对基本数据类型进行值传递，对引用数据类型开辟一个新的内存地址去存储拷贝的数据

来源：CSDN

作者：❤️大米花❤️

链接：https://blog.csdn.net/qq_28032223/article/details/104036435

标签

原型模式

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