Making a hash of hashes

Question

hi,
I am trying to make a hash of hashes to store various runtime attributes. This hash of hashes is stored in an object that is accessed by multiple server threads as well as being accessed by a timer thread every two minutes.
The data is of the form:
{user}
        {last_in}
        {status}
        {message}
                     {messageID}
                     {messageID}where {} denotes a hash key. So essentially the first hash has the users as the keys. Each user has a hash (again) for their particular attributes and we also have a message list.
My first run at this object was to have this message list as a hash but I am having problems adding a message. I can add the message but when the function call is left, the message no longer appears in the data structure.
Thinking this was a reference problem I managed to do the 'put' in one line as well so to avoid any temporary variables. Sadly this still didn't work.
Initially I am using Hashtables. I'm sure I'm missing something obvious ;)
Code follows, I'm still working on it so the comments aren't finished. Pertinent though are the functions addUser, addMessage and getMessageList:
// ==========================================================================
// Class:               Server Data Storage
// Lead Developer:     Simon Proctor
// Module filename: DataObject.java
// Module package:     ark.util.command
// Version                 Author           Date          Comment
// =========            ========     ========     ===============
// 1.0                      Simon          04/09/01     Initial Build
// Notes
// ===========================
// Abstracts the data storage away from the server so that the implementation
// and storage are separate.
// ==========================================================================
package ark.util.command;
import java.util.*;
public class DataObject
     // Class variables
     private static final Hashtable datastore = new Hashtable();
     private int messagecount = 1;
     public DataObject()
     public Set keySet()
          return this.datastore.keySet();
     public synchronized Object getData(String key)
          return  datastore.get(key);
     public synchronized boolean exists(String key)
          if(datastore.contains(key))
               return true;
          else
               return false;
     public synchronized void setData(String key, String value)
          datastore.put(key,value);
     public synchronized void addUser(String user)
          datastore.put(user,
               new Hashtable()
          Hashtable temp = (Hashtable) datastore.get(user);
          temp.put(new String("status"),"online");
          temp.put(new String("message"),new Hashtable());
          lastIn(user);
     public synchronized void addMessage(String user, String message)
          if(! exists(user))
               addUser(user);
          lastIn(user);
          messagecount++;
          Hashtable users = new Hashtable((Hashtable)datastore.get(user));
          Hashtable messages = new Hashtable((Hashtable)users.get("message"));
          Integer tempcount = new Integer(messagecount);
          messages.put(new String(tempcount.toString()),message);
          //((Hashtable)((Hashtable)datastore.get(user)).get("message")).put(new String(tempcount.toString()),message);
          System.out.println("Just tried :" + messagecount + " " + message);
          Enumeration print_test = messages.keys();
          while(print_test.hasMoreElements())
               String index = (String)print_test.nextElement();
               System.out.println(index + " " + messages.get(index));
     public synchronized String getMessage(String user, int messageID)
          if(! exists(user))
               addUser(user);
          lastIn(user);
          Hashtable users = (Hashtable)datastore.get(user);
          Hashtable messages = (Hashtable)users.get("message");
          String msg = (String)messages.get(new Integer(messageID));
          messages.remove(new Integer(messageID));
          return msg;
     public synchronized String getMessageList(String user)
          if(! exists(user))
               addUser(user);
          lastIn(user);
System.out.println("Looking at list for: " + user);
          Hashtable users = (Hashtable)datastore.get(user);
          Hashtable messages = (Hashtable)users.get("message");
          Enumeration message_set = messages.keys();
          StringBuffer temp = new StringBuffer();
          // Debug print
          Enumeration print_test = users.keys();
          while(print_test.hasMoreElements())
               System.out.println(print_test.nextElement());
          while(message_set.hasMoreElements())
               String message = (String)message_set.nextElement();
System.out.println("got : " + message);
              temp.append(message);
               temp.append(",");
          String list = temp.toString();
System.out.println("We now have : " + list);
          if(list.endsWith(","))
               return list.substring(0,list.length() - 1);
          else
               return list;
     public synchronized void setStatus(String user, String status)
          if(! exists(user))
               addUser(user);
          lastIn(user);
          Hashtable temp = (Hashtable)datastore.get(user);
          temp.put("status",status);
     public synchronized String getUserList(String user)
          if(! exists(user))
               addUser(user);
          lastIn(user);
          Enumeration user_set = datastore.keys();
          StringBuffer temp = new StringBuffer();
          while(user_set.hasMoreElements())
               String index = (String)user_set.nextElement();
              temp.append(index);
               temp.append(",");
          String list = temp.toString();
          if(list.endsWith(","))
               return list.substring(0,list.length() - 1);
          else
               return list;
     public synchronized void removeUser(String user)
          datastore.remove(user);
     private synchronized void lastIn(String user)
          // Set the last used status
          Date now = new Date();
          long time = now.getTime();
          Hashtable users = (Hashtable)datastore.get(user);
          users.put("last_in",new Long(time));
}

Answer 1

I tried the following
     public synchronized void addMessage(String user, String message)
          if(! exists(user))
               addUser(user);
          lastIn(user);
          messagecount++;
          Hashtable users = (Hashtable)datastore.get(user);
          Hashtable messages = (Hashtable)users.get("message");
          Integer tempcount = new Integer(messagecount);
          messages.put(new String(tempcount.toString()),message);
          //((Hashtable)((Hashtable)datastore.get(user)).get("message")).put(new String(tempcount.toString()),message);
          System.out.println("Just tried :" + messagecount + " " + message);
          Enumeration print_test = messages.keys();
          while(print_test.hasMoreElements())
               String index = (String)print_test.nextElement();
               System.out.println(index + " " + messages.get(index));
     }But still to no avail ;/.