原型模式
克隆羊问题
现在有一只羊tom,姓名:tom,年龄:1,颜色:白色,请编写程序创建和tom羊 属性完全相同的10只羊。
使用传统的方式的优缺点
1)优点时比较好理解,简单易操作。
2)在创建新的对象时,总是需要重新获取原始对象的属性,如果创建的对象比较复杂时,效率较低
3)总是需要重新初始化对象,而不是动态地获得对象运行时的状态,不够灵活
改进思路:在Java中Object类时所有类的基类,Object类提供了clone()方法,该方法可以将一个java类必须实现一个接口Cloneable,该接口表示该类能够复制且具有复制能力
原型模式-基本介绍
原型模式(Protorype模式)是指: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
原型模式时一种创建型设计模式,允许一个对象再创建另外一个可定制的对象,无需知道如何创建的细节
工作原理:通过将一个原型对象传给那个要发动创建的对象,这个要发动创建的对象啊你个通过请求原型对象拷贝它们自己来实施创建,即对象.clone()
形象的理解:孙大圣拔猴毛,变出其它孙猴子
1、浅拷贝
浅拷贝的介绍
对于数据原型时基本数据类型的成员变量,浅拷贝会直接进行值传递,也就是将该属性值复制一份给新的对象。
对于数据类型是引用数据类型的成员变量,比如说成员变量是某个数组、某个类的对象等等,那么浅拷贝会进行引用传递,也就是只是将成员变量的引用值(内存地址)复制一份给新的对象,因为实际上两个对象的该成员变量都指向同一个实例。在这种情况下,在一个对象中修改该成员变量会影响到另一个对象的成员变量值
浅拷贝使用默认的clone()方法实现即可
package designPatterns.protoType.type1;
//实现Cloneable接口,重写clone方法
public class Sheep implements Cloneable{
private String name;
private int age;
private String color;
public Sheep(){
}
public Sheep(String name,int age,String color){
this.name=name;
this.age=age;
this.color=color;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
@Override
public String toString() {
return "Sheep{" +
"name='" + name + '\'' +
", age=" + age +
", color='" + color + '\'' +
'}';
}
//重写clone方法
@Override
protected Object clone() throws CloneNotSupportedException {
//浅拷贝
return super.clone();
}
}
package designPatterns.protoType.type1;
public class TestMain {
public static void main(String[] args) throws CloneNotSupportedException {
Sheep sheep = new Sheep("绵阳", 19, "白色");
Sheep clone = (Sheep) sheep.clone();
Sheep clone1 = (Sheep) sheep.clone();
Sheep clone2 = (Sheep) sheep.clone();
Sheep clone3 = (Sheep) sheep.clone();
System.out.println(clone);
System.out.println(clone1);
System.out.println(clone2);
System.out.println(clone3);
}
}
2、深拷贝
深拷贝基本介绍
复制对象的所有基本数据类型的成员变量值
为所有引用数据类型的成员变量申请存储空间,并复制每个引用数据类型成员变量所引用的对象,知道该对象可达的所有对象。也就是说,对象进行深拷贝要对整个对象(包括对象的引用)进行拷贝
深拷贝实现方式1:重写clone方法来实现深拷贝
package designPatterns.protoType.type2;
//轮胎
public class Tyre implements Cloneable{
private String name;
private int age;
private String price;
public Tyre(){
}
public Tyre(String name,int age,String price){
this.name=name;
this.age=age;
this.price=price;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
@Override
public String toString() {
return "Tyre{" +
"name='" + name + '\'' +
", age=" + age +
", price='" + price + '\'' +
'}';
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
package designPatterns.protoType.type2;
public class Car implements Cloneable{
private String type;
private int age;
private String price;
private Tyre tyre;
public Car(){
}
public Car(String type,int age,String price,Tyre tyre){
this.type=type;
this.age=age;
this.price=price;
this.tyre=tyre;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
public Tyre getTyre() {
return tyre;
}
public void setTyre(Tyre tyre) {
this.tyre = tyre;
}
@Override
public String toString() {
return "Car{" +
"type='" + type + '\'' +
", age=" + age +
", price='" + price + '\'' +
", tyre=" + tyre +
'}';
}
//深拷贝(对引用的属性在进行克隆)
@Override
protected Object clone() throws CloneNotSupportedException {
//这里完成对基本数据类型和String类型进行clone
Car carClone = (Car) super.clone();
//对引用数据类型的属性,进行单独的clone
carClone.tyre= (Tyre) this.tyre.clone();
return carClone;
}
}
package designPatterns.protoType.type2;
public class TestMain {
public static void main(String[] args) throws CloneNotSupportedException {
Car car = new Car("宝马", 19, "1888888", new Tyre("好轮胎", 19, "3999"));
Car clone1 = (Car) car.clone();
Car clone2 = (Car) car.clone();
System.out.println(clone1==clone2);
System.out.println(clone1.hashCode() +""+ clone1);
System.out.println(clone2.hashCode() +""+ clone2);
}
}
2、深拷贝(对象序列化)
通过对象序列化实现深拷贝
类实现Serializable接口和Cloneable接口
重写clone方法
package designPatterns.protoType.type3;
import java.io.Serializable;
//轮胎
public class Tyre implements Cloneable, Serializable {
private String name;
private int age;
private String price;
private static final long serialVersionUID = 1L;
public Tyre(){
}
public Tyre(String name,int age,String price){
this.name=name;
this.age=age;
this.price=price;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
@Override
public String toString() {
return "Tyre{" +
"name='" + name + '\'' +
", age=" + age +
", price='" + price + '\'' +
'}';
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
package designPatterns.protoType.type3;
import java.io.*;
public class Car implements Cloneable, Serializable {
private String type;
private int age;
private String price;
private Tyre tyre;
private static final long serialServiceUID = 1L;
public Car() {
}
public Car(String type, int age, String price, Tyre tyre) {
this.type = type;
this.age = age;
this.price = price;
this.tyre = tyre;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPrice() {
return price;
}
public void setPrice(String price) {
this.price = price;
}
public Tyre getTyre() {
return tyre;
}
public void setTyre(Tyre tyre) {
this.tyre = tyre;
}
@Override
public String toString() {
return "Car{" +
"type='" + type + '\'' +
", age=" + age +
", price='" + price + '\'' +
", tyre=" + tyre +
'}';
}
//深拷贝(使用序列化+对象流)
@Override
protected Object clone() throws CloneNotSupportedException {
ByteArrayOutputStream bos = null;//字节输出流
ObjectOutputStream ops = null;//对象输出流
ByteArrayInputStream bis = null;//字节输入流
ObjectInputStream ois = null;//对象输入流
Car car = null;
try {
//对象序列化
bos = new ByteArrayOutputStream();
ops = new ObjectOutputStream(bos);
ops.writeObject(this);
//对象反序列化
bis = new ByteArrayInputStream(bos.toByteArray());
ois = new ObjectInputStream(bis);
car = (Car) ois.readObject();
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
return null;
} finally {
//关闭流
try {
ois.close();
bis.close();
ops.close();
bos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return car;
}
}
package designPatterns.protoType.type3;
public class TestMain {
public static void main(String[] args) throws CloneNotSupportedException {
Car car = new Car("宝马", 19, "1888888", new Tyre("好轮胎", 19, "3999"));
Car clone1 = (Car) car.clone();
Car clone2 = (Car) car.clone();
System.out.println(clone1==clone2);
System.out.println(clone1.hashCode() +""+ clone1);
System.out.println(clone2.hashCode() +""+ clone2);
}
}
原型模式的注意事项和细节
1)创建新的对象比较复杂时,可以利用原型模式简单化对象的创建过程,同时也能够提高效率
2)不用重新初始化对象,而是动态的获得对象运行时的状态
3)如果原始对象发生变化(增加或者减少属性),其他克隆对象的也会发生相应的变化,无需修改代码
4)在实现克隆的时候可能需要比较复杂的代码
5)缺点:需要为每一个类配备一个克隆方法,这对全新的类来说不是很难,但对已有的类进行改造时,需要修改其源代码,违背了ocp原则。
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