好的版式设计网站百度seo自然优化
1 基本概念
1.1 大佬文章
设计模式是什么鬼(原型)
详解设计模式:原型模式-腾讯云开发者社区-腾讯云
1.2 知识汇总
(1)原型模式:先 new 一个实例,该实例符合需求,之后再根据这个实例为原型,重复构建新的对象;
(2)所属类型:创建型模式
(3)作用:重复创建对象;
(4)优点:可以重复获得对象的同时保持较高的性能;
1.3 基本构成
(1)抽象原型类:抽象原型类是定义具有克隆自己的方法接口,是所有具体原型类的公共父类,可以是抽象类,也可以是接口;在 Java 中 Cloneable 接口可以看作是抽象原型类;
(2)具体原型类:根据这个类可以获得一个原型对象,并且这个类中需要重现 clone 方法,可以根据这个 clone 方法复制对象;
(3)访问类:使用具体原型类中的 clone 方法,可以不断重复的复制对象;
2 Java 中的克隆
根据现有的对象复制一个新的对象的操作就是克隆,Java 中克隆分为浅克隆和深克隆(我个人更喜欢说浅拷贝和深拷贝);浅拷贝和深拷贝的区别主要在重写 clone 方法上有所区别;但是,虽然之前有了解过拷贝的相关问题,但是发今天发现其实这里面还是有一些细节需要注意的。
2.1 拷贝的必要条件
(1)实现 Cloneable 接口:这个接口其实是一个标记接口,想要使用 clone 方法,就必须先实现这个接口,否则该类的 clone 方法是不可用的。
(2)重写 clone 方法:仅仅实现 Cloneable 接口还不能达到要求,还需要重写这个方法,否则依然不能使用 clone 方法;
2.2 浅拷贝
浅拷贝是将某个对象的所有成员属性都赋值给 clone 得到的对象;
(1)简单数据类型,如 int 等等的数据类型,直接将值拷贝过去;
(2)非简单数据类型,如引用类型的数据,是将引用的地址赋值给拷贝得到的对象,也就是说并没有新建一个成员对象,而是简单的将引用复制一遍;
package se.wangs.clonedemo.pojo;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 9:07* @description 演示浅拷贝*/
public class Teacher {private String name;private String idNo;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getIdNo() {return idNo;}public void setIdNo(String idNo) {this.idNo = idNo;}
}
package se.wangs.clonedemo.pojo;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 9:08* @description 演示clone*/
public class Student implements Cloneable{private String idNo;private String name;private Teacher teacher;public String getIdNo() {return idNo;}public void setIdNo(String idNo) {this.idNo = idNo;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}@Overridepublic Student clone() {try {Student clone = (Student) super.clone();// TODO: copy mutable state here, so the clone can't change the internals of the originalreturn clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}
package se.wangs.clonedemo;import se.wangs.clonedemo.pojo.Student;
import se.wangs.clonedemo.pojo.Teacher;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/4 16:37* @description 浅拷贝*/
public class ShallowClone {public static void main(String[] args) {Teacher teacher1 = new Teacher();teacher1.setIdNo("001");teacher1.setName("teacher_001");Student student1 = new Student();student1.setIdNo("101");student1.setName("student_101");student1.setTeacher(teacher1);Student cloneStudent = student1.clone();System.out.println("---------------------------");System.out.println(student1);System.out.println("idNo = " + student1.getIdNo());System.out.println("name = " + student1.getName());System.out.println("teacher = " + student1.getTeacher());System.out.println("---------------------------");System.out.println(cloneStudent);System.out.println("idNo = " + cloneStudent.getIdNo());System.out.println("name = " + cloneStudent.getName());System.out.println("teacher = " + cloneStudent.getTeacher());}
}
运行测试类得到的结果如下:
---------------------------
se.wangs.clonedemo.pojo.Student@41629346
idNo = 101
name = student_101
teacher = se.wangs.clonedemo.pojo.Teacher@214c265e
---------------------------
se.wangs.clonedemo.pojo.Student@448139f0
idNo = 101
name = student_101
teacher = se.wangs.clonedemo.pojo.Teacher@214c265e
说明:
- student1:原对象
- cloneStudent:浅拷贝得到的对象
可以看到,student 中有一个引用类型的成员变量 teacher,浅拷贝得到的 cloneStudent 中的 teacher 变量与 student1 指向的对象相同;
2.3 深拷贝
深拷贝就是会将引用类型的变量做进一步处理,clone 出的对象的引用数据类型的成员变量,会指向一个新的变量
package se.wangs.clonedemo.pojo;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 9:07* @description 演示浅拷贝*/
public class Teacher implements Cloneable{private String name;private String idNo;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getIdNo() {return idNo;}public void setIdNo(String idNo) {this.idNo = idNo;}@Overridepublic Teacher clone() {try {Teacher clone = (Teacher) super.clone();// TODO: copy mutable state here, so the clone can't change the internals of the originalreturn clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}
package se.wangs.clonedemo.pojo;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 9:08* @description 演示clone*/
public class Student implements Cloneable{private String idNo;private String name;private Teacher teacher;public String getIdNo() {return idNo;}public void setIdNo(String idNo) {this.idNo = idNo;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}@Overridepublic Student clone() {try {Student clone = (Student) super.clone();// 获得原来的 teacher 对象,并clone出一个新的teacher对象Teacher newTeacher = clone.getTeacher().clone();// 重新设置teacherclone.setTeacher(newTeacher);return clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}
package se.wangs.clonedemo;import se.wangs.clonedemo.pojo.Student;
import se.wangs.clonedemo.pojo.Teacher;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 10:09* @description 深拷贝*/
public class DeepClone {public static void main(String[] args) {Teacher teacher1 = new Teacher();teacher1.setIdNo("001");teacher1.setName("teacher_001");Student student1 = new Student();student1.setIdNo("101");student1.setName("student_101");student1.setTeacher(teacher1);Student cloneStudent = student1.clone();System.out.println("---------------------------");System.out.println(student1);System.out.println("idNo = " + student1.getIdNo());System.out.println("name = " + student1.getName());System.out.println("teacher = " + student1.getTeacher());System.out.println("---------------------------");System.out.println(cloneStudent);System.out.println("idNo = " + cloneStudent.getIdNo());System.out.println("name = " + cloneStudent.getName());System.out.println("teacher = " + cloneStudent.getTeacher());}
}
运行得到
---------------------------
se.wangs.clonedemo.pojo.Student@41629346
idNo = 101
name = student_101
teacher = se.wangs.clonedemo.pojo.Teacher@214c265e
---------------------------
se.wangs.clonedemo.pojo.Student@448139f0
idNo = 101
name = student_101
teacher = se.wangs.clonedemo.pojo.Teacher@7cca494b
可以看到,得到的 teacher 对象的地址变了;
2.4 总结
浅拷贝和深拷贝的主要区别就是对引用类型的变量的处理
(1)浅拷贝:引用类型的变量拷贝前后指向同一个对象;
(2)深拷贝:引用类型的变量拷贝后指向新的对象;
(3)核心:重写 clone 方法时对引用类型变量的处理不同;
参考资料:
Java深入理解深拷贝和浅拷贝区别_java深拷贝浅拷贝-CSDN博客
3 原型设计模式
3.1 设计模式体验
(1)抽象原型类:Cloneable 接口
(2)具体原型类:可以 new 原型实例,实现 Cloneable 接口,重写了 clone() 方法;
package se.wangs.prototype;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 9:07* @description*/
public class Teacher implements Cloneable{private String name;private String idNo;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getIdNo() {return idNo;}public void setIdNo(String idNo) {this.idNo = idNo;}@Overridepublic Teacher clone() {try {Teacher clone = (Teacher) super.clone();// TODO: copy mutable state here, so the clone can't change the internals of the originalreturn clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}
package se.wangs.prototype;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 9:08* @description 具体原型类*/
public class Student implements Cloneable{private String idNo;private String name;private Teacher teacher;public String getIdNo() {return idNo;}public void setIdNo(String idNo) {this.idNo = idNo;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}@Overridepublic Student clone() {try {Student clone = (Student) super.clone();// 获得原来的 teacher 对象,并clone出一个新的teacher对象Teacher newTeacher = clone.getTeacher().clone();// 重新设置teacherclone.setTeacher(newTeacher);return clone;} catch (CloneNotSupportedException e) {throw new AssertionError();}}
}
(3)访问类:实例化原型,通过 clone 复制原型对象;
package se.wangs.prototype;/*** -- coding: UTF-8 -- *** @author wangs* @date 2023/12/6 10:30* @description 访问类*/
public class Client {public static void main(String[] args) {Teacher teacher = new Teacher();teacher.setName("okay");teacher.setIdNo("0001");Student student = new Student();student.setIdNo("stu_001");student.setName("onesun");student.setTeacher(teacher);System.out.println("---------------------------");System.out.println(student);System.out.println("idNo = " + student.getIdNo());System.out.println("name = " + student.getName());System.out.println("teacher = " + student.getTeacher());for (int i = 0; i < 10; i++) {System.out.println("---------------------------");Student cloneStudent = student.clone();System.out.println(cloneStudent);System.out.println("idNo = " + cloneStudent.getIdNo());System.out.println("name = " + cloneStudent.getName());System.out.println("teacher = " + cloneStudent.getTeacher());}}
}
3.2 总结
(1)原型设计模式的思想就是拿到一个对象,将该对象当作一个标准,然后使用 clone 方法不断重复的去复制这个标准(原型对象),从而得到大量同类型的对象,在游戏等等场景中应用广泛。
(2)使用原型模式而不是 new 对象的优点是,节约 new 需要消耗的资源,提高系统的性能。
(3)原型模式的应用
Spring 框架对 bean 对象进行管理,而默认的 bean 对象是单例模式的,也可以使用 scope 属性指定为非单例模式,当 scope 属性为"socpe=prototype"
时,就是非单例模式,其实这里使用的就是原型模式;