原型模式
原型模式(Prototype Pattern)是用于创建重复的对象,同时又能保证性能。这种类型的设计模式属于创建型模式,它提供了一种创建对象的最佳方式。
这种模式是实现了一个原型接口,该接口用于创建当前对象的克隆。当直接创建对象的代价比较大时,则采用这种模式。
浅克隆
package com.cyc.design.prototype.v1;
/**
* 浅克隆
*/
public class Test {
public static void main(String[] args) throws Exception {
Person p1 = new Person();
Person p2 = (Person)p1.clone();
System.out.println(p2.age + " " + p2.score);
System.out.println(p2.loc);
System.out.println(p1.loc == p2.loc);
//由于这里实现的浅克隆,p2中loc属性的引用和p1中的loc指向的是同一个地址,
//因此,p1的loc.street值改变之后, 会影响p2.loc
p1.loc.street = "sh";
System.out.println(p2.loc);
}
}
class Person implements Cloneable {
int age = 8;
int score = 100;
Location loc = new Location("bj", 22);
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
class Location {
String street;
int roomNo;
@Override
public String toString() {
return "Location{" +
"street='" + street + '\'' +
", roomNo=" + roomNo +
'}';
}
public Location(String street, int roomNo) {
this.street = street;
this.roomNo = roomNo;
}
}
深克隆
package com.cyc.design.prototype.v2;
/**
* 深克隆的处理
*/
public class Test {
public static void main(String[] args) throws Exception {
Person p1 = new Person();
Person p2 = (Person)p1.clone();
System.out.println(p2.age + " " + p2.score);
System.out.println(p2.loc);
System.out.println(p1.loc == p2.loc);
p1.loc.street = "sh";
System.out.println(p2.loc);
}
}
class Person implements Cloneable {
int age = 8;
int score = 100;
Location loc = new Location("bj", 22);
@Override
public Object clone() throws CloneNotSupportedException {
Person p = (Person)super.clone();
p.loc = (Location)loc.clone();
return p;
}
}
/**
* 这里让Location同样实现Cloneable接口,在Person克隆是,里面的属性location同样也克隆一份
* 此时p2中的location和p1中的location便不再是同一个
*/
class Location implements Cloneable {
String street;
int roomNo;
@Override
public String toString() {
return "Location{" +
"street='" + street + '\'' +
", roomNo=" + roomNo +
'}';
}
public Location(String street, int roomNo) {
this.street = street;
this.roomNo = roomNo;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
字符串需要深克隆吗
package com.cyc.design.prototype.v3;
/**
* String需要进一步深克隆吗?
*/
public class Test {
public static void main(String[] args) throws Exception {
Person p1 = new Person();
Person p2 = (Person)p1.clone();
System.out.println(p2.age + " " + p2.score);
System.out.println(p2.loc);
System.out.println(p1.loc == p2.loc);
p1.loc.street = "sh";
System.out.println(p2.loc);
p1.loc.street.replace("sh", "sz");
System.out.println(p2.loc.street);
}
}
class Person implements Cloneable {
int age = 8;
int score = 100;
Location loc = new Location("bj", 22);
@Override
public Object clone() throws CloneNotSupportedException {
Person p = (Person)super.clone();
p.loc = (Location)loc.clone();
return p;
}
}
class Location implements Cloneable {
//因为String类型指向的本来就一个常量池, 常量池中有bj和sh,
// 第一个p1中的loc.street指向的是常量池中的bj,克隆出来的p2中的loc.street指向的也是bj
// 虽然p1.loc.street和p2.loc.street指向的都是常量池中同一个bj,
// 改变p1里面的内容,让其指向sh,但是克隆出来的那个p2依然指向的是bj, 因此字符串不需要深克隆
String street;
int roomNo;
@Override
public String toString() {
return "Location{" +
"street='" + street + '\'' +
", roomNo=" + roomNo +
'}';
}
public Location(String street, int roomNo) {
this.street = street;
this.roomNo = roomNo;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
StringBuilder 克隆
package com.cyc.design.prototype.v4;
/**
* String需要进一步深克隆吗?
*/
public class Test {
public static void main(String[] args) throws Exception {
Person p1 = new Person();
Person p2 = (Person)p1.clone();
System.out.println("p1.loc == p2.loc? " + (p1.loc == p2.loc));
//由于p1和p2中的StringBuilder对象指向的是同一个地址
//所以p1的StringBuilder对象变了之后, p2的也会跟着边
p1.loc.street.reverse();
System.out.println(p2.loc.street);
}
}
class Person implements Cloneable {
int age = 8;
int score = 100;
Location loc = new Location(new StringBuilder("bj"), 22);
@Override
public Object clone() throws CloneNotSupportedException {
Person p = (Person)super.clone();
p.loc = (Location)loc.clone();
return p;
}
}
class Location implements Cloneable {
StringBuilder street;
int roomNo;
@Override
public String toString() {
return "Location{" +
"street='" + street + '\'' +
", roomNo=" + roomNo +
'}';
}
public Location(StringBuilder street, int roomNo) {
this.street = street;
this.roomNo = roomNo;
}
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}