来人啊，看看这个小程序什么问题

Question

import java.io.*;public class Try
{
  public static void main(String args[]) throws Exception
  {
    FileOutputStream fout=new FileOutputStream("E:\\qq.txt",true);
    ObjectOutputStream oout=new ObjectOutputStream(fout);
    Client client=new Client(8,"hijilmn");
    oout.writeObject(client);
    Client client2=new Client(3,"wuwenyu");
    oout.writeObject(client);
    oout.close();
    fout.close();    FileInputStream fin=new FileInputStream("E:\\qq.txt");
    ObjectInputStream oin=new ObjectInputStream(fin);
    Client client3=(Client)oin.readObject();
    System.out.println(client3);
    client3=(Client)oin.readObject();
    System.out.println(client3);
    oin.close();
    fin.close();
  }
}class Client implements Serializable
{
  public int num;
  public String name;  public Client(int num,String name)
  {
    this.num=num;
    this.name=name;
  }  public String toString()
  {
    return "num="+num+", name="+name;
  }
}
为什么输出的是同一个人名？输出如下：
num=8,name=hijilmn
num=8,name=hijilmn

Answer 1

Client client3=(Client)oin.readObject(); 
    System.out.println(client3); 
    client3=(Client)oin.readObject(); 
    System.out.println(client3); 
这两句好像一样啊，都是client3

Answer 2

 //发表于：2008-11-28 23:27:45 楼主 
import java.io.*; public class Try 
{ 
  public static void main(String args[]) throws Exception 
  { 
    FileOutputStream fout=new FileOutputStream("E:\\qq.txt"); 
    ObjectOutputStream oout=new ObjectOutputStream(fout); 
    Client client1=new Client(8,"hijilmn"); 
    oout.writeObject(client1); 
    Client client2=new Client(3,"wuwenyu"); 
    oout.writeObject(client2); 
    oout.close(); 
    fout.close();     FileInputStream fin=new FileInputStream("E:\\qq.txt"); 
    ObjectInputStream oin=new ObjectInputStream(fin); 
    Client client3=(Client)oin.readObject(); 
    System.out.println(client3); 
    Client client4=(Client)oin.readObject(); 
    System.out.println(client4); 
    oin.close(); 
    fin.close(); 
  } 
} class Client implements Serializable 
{ 
  public int num; 
  public String name;   public Client(int num,String name) 
  { 
    this.num=num; 
    this.name=name; 
  }   public String toString() 
  { 
    return "num="+num+", name="+name; 
  } 
} 
 
 

Answer 3

Client client=new Client(8,"hijilmn"); 
    oout.writeObject(client); 
    Client client2=new Client(3,"wuwenyu"); 
    oout.writeObject(client); //client改为client2

Answer 4

import java.io.*; public class Try 
{ 
  public static void main(String args[]) throws Exception 
  { 
    FileOutputStream fout=new FileOutputStream("E:\\qq.txt",true); 
    ObjectOutputStream oout=new ObjectOutputStream(fout); 
    Client client=new Client(8,"hijilmn"); 
    oout.writeObject(client); 
    Client client2=new Client(3,"wuwenyu"); 
    //很明显,这里错了,两次writeObject都写进的是一样的,改成client2就成了.....
    oout.writeObject(client2); 
    oout.close(); 
    fout.close();     FileInputStream fin=new FileInputStream("E:\\qq.txt"); 
    ObjectInputStream oin=new ObjectInputStream(fin); 
    Client client3=(Client)oin.readObject(); 
    System.out.println(client3); 
    client3=(Client)oin.readObject(); 
    System.out.println(client3); 
    oin.close(); 
    fin.close(); 
  } 
} 

Answer 5

我改了怎么是两个名字public class test
{
  public static void main(String args[]) throws Exception
  {
    FileOutputStream fout=new FileOutputStream("E:\\qq.txt",true);
    ObjectOutputStream oout=new ObjectOutputStream(fout);
    Client client=new Client(8,"hijilmn");
    oout.writeObject(client);
    Client client2=new Client(3,"wuwenyu");
    oout.writeObject(client2);
    oout.close();
    fout.close();    FileInputStream fin=new FileInputStream("E:\\qq.txt");
    ObjectInputStream oin=new ObjectInputStream(fin);
    Client client3=(Client)oin.readObject();
    System.out.println(client3);
    client3=(Client)oin.readObject();
    System.out.println(client3);
    oin.close();
    fin.close();
  }
}class Client implements Serializable
{
  public int num;
  public String name;  public Client(int num,String name)
  {
    this.num=num;
    this.name=name;
  }  public String toString()
  {
    return "num="+num+", name="+name;
  }
} num=8, name=hijilmn
num=3, name=wuwenyu

Answer 6

FileOutputStream fout=new FileOutputStream("E:\\qq.txt"); 
改成下面的这样：
FileOutputStream fout=new FileOutputStream("E:\\qq.txt",true);
这样才能保证下次写入的东西不会覆盖前面写入的东西，当用了true后，就是在你前一次写入的后面添加新的信息而不覆盖原始的信息，如果不写true的话，系统默认为FALSE，覆盖原始的信息！！！
这个小问题需要多多注意，其实你改不改变client无所谓，因为当你new一个新对象的时候分配的内存地址是不同的，jvm还是能找到相应的对象；当然这样写别人不容易看懂你写的程序，不建议这样写！！！