【java开发系列】—— 深克隆和浅克隆

　　Java支持我们对一个对象进行克隆，通常用在装饰模式和原型模式中。那么什么是深克隆，什么是浅克隆呢。

　　【浅克隆】，通常只是对克隆的实例进行复制，但里面的其他子对象，都是共用的。

　　【深克隆】，克隆的时候会复制它的子对象的引用，里面所有的变量和子对象都是又额外拷贝了一份。

　　下面的两个例子可以很好的说明他们的区别：

　　首先看一下类图

　　Husband类有一个对wife的引用，当进行浅克隆的时，wife变量都会指向同一个Wife；而进行深克隆时，会指向不同的Wife。下面进行一下验证：

　　【浅克隆】

 public Object clone() {
         Husband husband = null;
         try{
             husband = (Husband)super.clone();
         }catch(CloneNotSupportedException e){
             e.printStackTrace();
         }finally{
             return husband;
         }
     }

　　【深克隆】

 public Object deepClone() throws IOException,ClassNotFoundException {
         //将对象写到流里
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         ObjectOutputStream oos = new ObjectOutputStream(bos);
         oos.writeObject(this);
         //从流里读回来
         ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
         ObjectInputStream ois = new ObjectInputStream(bis);
         return ois.readObject();
     }

　　【全部代码】

 package com.xingoo.clone;

 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;
 import java.util.Date;

 class Wife implements Serializable{
     private String name;
     private Date birthday;

     public Wife(){
         name = "芙蓉姐姐";
         birthday = new Date();
     }
     public Date getBirthday(){
         return birthday;
     }

     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
 }
 class Husband implements Cloneable,Serializable{
     private Wife wife;
     private Date birthday;

     public Husband(){
         wife = new Wife();
         birthday = new Date();
     }

     public Wife getWife(){
         return wife;
     }

     public Date getBirthday(){
         return birthday;
     }
     /**
      * 浅克隆一个对象
      */
     public Object clone() {
         Husband husband = null;
         try{
             husband = (Husband)super.clone();
         }catch(CloneNotSupportedException e){
             e.printStackTrace();
         }finally{
             return husband;
         }
     }
     /**
      * 利用串行化深克隆一个对象，把对象以及它的引用读到流里，在写入其他的对象
      * @return
      * @throws IOException
      * @throws ClassNotFoundException
      */
     public Object deepClone() throws IOException,ClassNotFoundException {
         //将对象写到流里
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         ObjectOutputStream oos = new ObjectOutputStream(bos);
         oos.writeObject(this);
         //从流里读回来
         ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
         ObjectInputStream ois = new ObjectInputStream(bis);
         return ois.readObject();
     }
 }
 public class Test {
     public static void main(String[] args){
         try{
             Husband husband = new Husband();
             System.out.println("husband birthday "+husband.getBirthday().getTime());
             System.out.println("wife birthday "+husband.getWife().getBirthday().getTime());
             System.out.println();
             Husband husband1 = (Husband)husband.clone();
             System.out.println("husband1 birthday "+husband1.getBirthday().getTime());
             System.out.println("wife birthday "+husband1.getWife().getBirthday().getTime());
             System.out.println();
             System.out.println("是否是同一个husband "+(husband == husband1));
             System.out.println("是否是同一个wife "+ (husband.getWife() == husband1.getWife()));
             System.out.println();
             Husband husband2 = (Husband)husband.deepClone();
             System.out.println("husband2 birthday "+husband2.getBirthday().getTime());
             System.out.println("wife birthday "+husband2.getWife().getBirthday().getTime());
             System.out.println();
             System.out.println("是否是同一个husband "+(husband == husband2));
             System.out.println("是否是同一个wife "+ (husband.getWife() == husband2.getWife()));
         }catch(Exception e){
             e.printStackTrace();
         }
     }
 }

　　【运行结果】

husband birthday
wife birthday 

husband1 birthday
wife birthday
是否是同一个husband false
是否是同一个wife true

husband2 birthday
wife birthday
是否是同一个husband false
是否是同一个wife false