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;

      }

}