Hi, I am encountering a strange problem with a client/server socket
program. In a tight loop, I am changing a field of an object and then
sending it over a socket. However, the change is not evident at the
receiving socket at the other end! This problem occurs with the
client/server pair on the same machine.

My code looks like this:

public class Datum implements java.io.Serializable
{
 public String _data;
 Datum() { }
}

In the sending program, I have this code:
       Datum data = new Datum();
       for (int i = 0; i < 10; i++)
       {
               data._data = "data"+i;
               System.out.println("sending " + data._data);
               oos.writeObject(data);
               oos.flush();
       }

At the sender, this properly prints data1, data2, data3, etc.
However, at the other end of the socket, I am getting data1, data1,
data1, etc.
When I instantiate 'new Datum' inside the loop, it works properly.

Does anyone have an idea?

Below is all the source code.

public class Datum implements java.io.Serializable
{
 public String _data;
 Datum() { }
}

import java.io.*;
import java.net.*;

class Client
{
 public static void main(String argv[])
 {
   try
   {
       Socket socket = new Socket("localhost", 3000);
       ObjectInputStream ois = new
ObjectInputStream(socket.getInputStream());

       Datum data;
       for (int i = 0; i < 10; i++)
       {
               data = (Datum) ois.readObject();
               System.out.println("got '"+data._data+"'");
       }
   }
   catch(Exception ex)
   {
       //System.out.println(ex);
       ex.printStackTrace();
   }
 }
}

import java.io.*;
import java.net.*;

public class Server
{
 public static void main(String argv[])
 {
       //send_method_1(); // THIS ONE WORKS
       send_method_2(); // THIS ONE DOESN'T WORK!!
 }

/*********************************************************************/
 static void send_method_1()
 {
    try
    {
       ServerSocket socket = new ServerSocket(3000);
       System.out.println("waiting for connection");
       Socket client_socket = socket.accept();

       ObjectOutputStream oos =
               new
ObjectOutputStream(client_socket.getOutputStream());

       for (int i = 0; i < 10; i++)
       {
               Datum data = new Datum();
               data._data = "data"+i;
               System.out.println("sending " + data._data);
               oos.writeObject(data);
               oos.flush();
       }
   }
   catch(Exception ex)
   {
       //System.out.println(ex);
       ex.printStackTrace();
   }
 }

/*********************************************************************/
 static void send_method_2()
 {
    try
   {
       ServerSocket socket = new ServerSocket(3000);
       System.out.println("waiting for connection");
       Socket client_socket = socket.accept();

       ObjectOutputStream oos =
               new
ObjectOutputStream(client_socket.getOutputStream());

       Datum data = new Datum();
       for (int i = 0; i < 10; i++)
       {
               data._data = "data"+i;
               System.out.println("sending " + data._data);
               oos.writeObject(data);
               oos.flush();
       }
   }
   catch(Exception ex)
   {
       //System.out.println(ex);
       ex.printStackTrace();
   }
 }
}