Java设计模式之原型模式（属于创建型模式）
Java设计模式之原型模式
模式定义：原型模式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。（用于对象的复制）
两个步骤：
- 在原型类上实现Cloneable接口。
- 再原型类中重写java.lang.Object类的clone()方法。
Student：
//1、实现Cloneable接口
public class Student implements Cloneable{
private Integer id;
private String name;
private String age;
public Student(Integer id,String name,String age){
this.id = id;
this.name = name;
this.age = age;
}
//生成getter() 和 setter() 方法
//2、重写clone()方法
@Override
protected Student clone() throws CloneNotSupportedException {
return (Student)super.clone();
}
@Override
public String toString() {
return super.hashCode() + " " +"Student{" +
"id=" + id +
", name='" + name + '\'' +
", age='" + age + '\'' +
'}';
}
}
test：
public class test1 {
public static void main(String[] args) throws CloneNotSupportedException {
Student student = new Student(1,"chenl","12");
Student student1 = student.clone();
Student student2 = student.clone();
System.out.println(student1.toString());
System.out.println(student2.toString());
}
}
但是，其对引用类型的拷贝则是浅拷贝（即拷贝引用，或者说拷贝地址值），下面是验证方法：
新建一个IDCard ：
public class IDCard{
private Integer id;
private String Number;
public IDCard(Integer id,String Number){
this.id = id;
this.Number = Number;
}
//生成getter()和 setter()方法
@Override
public String toString() {
return super.hashCode()+ " " + "IDCard{" +
"id=" + id +
", Number='" + Number + '\'' +
'}';
}
}
更改Student ：
class Student implements Cloneable{
private Integer id;
private String name;
private String age;
private IDCard idCard;
public Student(Integer id,String name,String age,IDCard idCard){
this.id = id;
this.name = name;
this.age = age;
this.idCard = idCard;
}
//生成getter() 和 setter()方法
@Override
protected Student clone() throws CloneNotSupportedException {
return (Student)super.clone();
}
@Override
public String toString() {
return super.hashCode() + " " +"Student{" +
"id=" + id +
", name='" + name + '\'' +
", age='" + age + '\'' +
", idCard=" + idCard +
'}';
}
}
测试类：
public class test1 {
public static void main(String[] args) throws CloneNotSupportedException {
IDCard idCard = new IDCard(1,"123");
Student student = new Student(1,"chenl","12",idCard);
Student student1 = student.clone();
Student student2 = student.clone();
System.out.println(student1.toString());
System.out.println(student2.toString());
idCard.setNumber("456");
System.out.println(student);
System.out.println(student1.toString());
System.out.println(student2.toString());
}
}
可以看出，student1和student2对象IDCard的Number值随着Student对象IDCard的值改变而改变，说明它们引用了同一个对象。
如果想要实现深拷贝，则需要在IDCard类上实现Cloneable接口并重写clone()方法。
更改IDCard：
//1、实现Cloneale接口
public class IDCard implements Cloneable{
private Integer id;
private String Number;
public IDCard(Integer id,String Number){
this.id = id;
this.Number = Number;
}
//生成getter() 和 setter()方法
//2、重写clone()方法
@Override
protected IDCard clone() throws CloneNotSupportedException {
return (IDCard) super.clone();
}
@Override
public String toString() {
return super.hashCode()+ " " + "IDCard{" +
"id=" + id +
", Number='" + Number + '\'' +
'}';
}
}
更改Student：
class Student implements Cloneable{
private Integer id;
private String name;
private String age;
private IDCard idCard;
public Student(Integer id,String name,String age,IDCard idCard){
this.id = id;
this.name = name;
this.age = age;
this.idCard = idCard;
}
//生成getter() 和 setter()方法
//重写clone()方法
@Override
protected Student clone() throws CloneNotSupportedException {
Student student = (Student) super.clone();
student.setIdCard(student.getIdCard().clone());
return student;
}
@Override
public String toString() {
return super.hashCode() + " " +"Student{" +
"id=" + id +
", name='" + name + '\'' +
", age='" + age + '\'' +
", idCard=" + idCard +
'}';
}
}
测试：
public class test1 {
public static void main(String[] args) throws CloneNotSupportedException {
IDCard idCard = new IDCard(1,"123");
Student student = new Student(1,"chenl","12",idCard);
Student student1 = student.clone();
Student student2 = student.clone();
idCard.setNumber("456");
System.out.println(student);
System.out.println(student1.toString());
System.out.println(student2.toString());
idCard.setNumber("456");
System.out.println(student);
System.out.println(student1.toString());
System.out.println(student2.toString());
}
}
如图，即使改变了idCard的 Number值，student1 和 student2的对应值并未发生改变，说明它们单独拷贝了一份数据。