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一.原型模式介绍
因为java中new一个新对象比clone一个对象需要花费等多的资源，所以一般需要
在短时间内创建大量对象并且new对象的过程需要耗费比较多的资源使用原型模式。
想要clone一个类需要这个类实现Cloneable接口，重载clone方法，这个接口在底层
通过内存拷贝实现clone对象，因此效率很高。
package com.lz.prototype;
import java.util.Date;
public class ShallowClone implements Cloneable{
private String name;
private int age;
private Date date;
public ShallowClone() {
}
public ShallowClone(String name, int age, Date date) {
super();
this.name = name;
this.age = age;
this.date = date;
}
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 Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
@Override
protected Object clone() throws CloneNotSupportedException {
Object obj = super.clone();
return obj;
}
}
package com.lz.prototype;
import java.util.Date;
public class ShallowTest {
public static void main(String[] args) {
ShallowClone sc1 = new ShallowClone("laro", 20, new Date());
System.out.println(sc1);
System.out.println(sc1.getName());
System.out.println(sc1.getAge());
System.out.println(sc1.getDate());
ShallowClone sc2 = null;
try {
sc2 = (ShallowClone) sc1.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
sc1.setDate(new Date());
System.out.println(sc2);
System.out.println(sc2.getName());
System.out.println(sc2.getAge());
System.out.println(sc2.getDate());
}
}
二.原型模式效率检测
下面是一个简单的效率测试
package com.lz.prototype;
public class Efficiency {
public static void main(String[] args) throws CloneNotSupportedException {
test01();
T s = new T();
test02(s);
}
public static void test01() {
long start = System.currentTimeMillis();
for ( int i=0; i<1000; i++ ) {
T s = new T();
}
long end = System.currentTimeMillis();
System.out.println((end-start)+"毫秒");
}
public static void test02(T s) throws CloneNotSupportedException {
long start = System.currentTimeMillis();
for ( int i=0; i<1000; i++ ) {
T copy = (T) s.clone();
}
long end = System.currentTimeMillis();
System.out.println((end-start)+"毫秒");
}
}
class T implements Cloneable{
public T() {
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
三.浅拷贝与深拷贝
下面是一个简单代码实现当然上面的代码只实现了浅拷贝，浅拷贝的含义是只clone这个对象本身，而这个类里面包含的其他引用对象并没有
实现clone。这里想要实现深拷贝需要改动代码
package com.lz.prototype; import java.util.Date; public class DeepClone implements Cloneable{ private String name; private int age; private Date date; public DeepClone() { } public DeepClone(String name, int age, Date date) { super(); this.name = name; this.age = age; this.date = date; } 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 Date getDate() { return date; } public void setDate(Date date) { this.date = date; } /* * 实现深拷贝 * @see java.lang.Object#clone() */ @Override protected Object clone() throws CloneNotSupportedException { Object obj = super.clone(); DeepClone dc = (DeepClone) obj; dc.date = (Date) this.date.clone(); return obj; } }
简单的实现深clone很简单，只需要将需要clone的类的内部的引用类也clone即可。
但是这种方法在比较复杂的类中就不容易实现了，这里还可以使用序列化和反序列化实现clone
当然一个类想实现序列化和反序列话需要实现Serializable接口
下面是一个简单的代码实现：
package com.lz.prototype; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.Date; /* * 序列化反序列化clone对象 */ public class Test01 { public static void main(String[] args) throws Exception { Sheep s1 = new Sheep("tom", new Date(1000000000L)); ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(s1); byte[] bytes = bos.toByteArray(); ByteArrayInputStream bis = new ByteArrayInputStream(bytes); ObjectInputStream ois = new ObjectInputStream(bis); Sheep s2 = (Sheep) ois.readObject(); System.out.println("测试前"); System.out.println(s1); System.out.println(s1.getName()+" " + s1.getBirthday()); System.out.println(s2); System.out.println(s2.getName()+" " + s2.getBirthday()); s1.setName("laro"); s1.setBirthday(new Date(1000000000L)); System.out.println("测试后"); System.out.println(s1); System.out.println(s1.getName()+" " + s1.getBirthday()); System.out.println(s2); System.out.println(s2.getName()+" " + s2.getBirthday()); } } class Sheep implements Cloneable, Serializable{ private String name; private Date birthday; public Sheep() { } public Sheep(String name, Date birthday) { super(); this.name = name; this.birthday = birthday; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } @Override protected Object clone() throws CloneNotSupportedException { return super.clone(); } }
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原文地址：http://www.cnblogs.com/larobyo/p/5293613.html
