Java SerialVersionUID作用详解

import  java.io.Serializable;
 
public  class  Person  implements  Serializable {
     
     //如果没有指定serialVersionUID，系统会自动生成一个
     private  static  final  long  serialVersionUID = 1L;
     private  String name;
     //添加这么一个成员变量  
     private  String address;    //序列化后如果之前版本没有，就为null
 
     public  String getName() {
//      int a = 100;
//      for(int i=0;i<a;i++){
//          name+=i;
//      }
         return  name;
     }
     public  void  setName(String name) {
         this .name = name;
     }
}

import  java.io.FileInputStream;
import  java.io.FileNotFoundException;
import  java.io.FileOutputStream;
import  java.io.IOException;
import  java.io.ObjectInputStream;
import  java.io.ObjectOutputStream;
 
/**
  * if Object implements Serializable without Uid,
  * system will automatically give this object a uid by algorithm
  * @author v11
  * @date 2014年9月18日
  * @version 1.0
  */
public  class  WhySerialversionUID {
 
     public  static  void  objectToFile(Object obj,String fileName)  throws  Exception{
         ObjectOutputStream oo =  new  ObjectOutputStream( new  FileOutputStream(
                 fileName));
         oo.writeObject(obj);
         oo.close();
     }
 
     public  static  Object getObjectFromFile(String fileName)  throws  Exception {
         ObjectInputStream oi =  new  ObjectInputStream( new  FileInputStream(
                 fileName));
         Person crab_back = (Person) oi.readObject();
         oi.close();
         return  crab_back;
     }
     public  static  void  main(String[] args)  throws  Exception {
         String fileName =  "crab_file" ; //文件名
         
         // 这里是把对象序列化到文件
         Person crab =  new  Person();
         crab.setName( "Mr.Crab" );
         
         //储存到文件中
         //objectToFile(crab,fileName);
 
         // 这里是把对象序列化到文件，我们先注释掉，一会儿用
         Person crabBack = (Person) getObjectFromFile(fileName);
         //Dog crabBack = (Dog) getObjectFromFile(fileName);
         System.out.println( "Hi, My name is "  + crabBack.getName());
 
     }
}

public  class  Dog  implements  Serializable{
     
     private  static  final  long  serialVersionUID = 1L;
     private  String name;
     
     public  String getName() {
         return  name;
     }
 
     public  void  setName(String name) {
         this .name = name;
     }
     
}