Possible Duplicate:
LAN chating system or LAN chat server

displaying list of user to all the user window my code is i m use RMI so this is the interface declaration

public void sendPublicMessage(String keyword, String username, String message) throws RemoteException;
public void sendPrivateMessage(String keyword, String username, String message) throws RemoteException;
public ArrayList getClientList() throws RemoteException;
public void connect(String username) throws RemoteException;
public void disconnect(String username) throws RemoteException;

}

chat Server here connectedUser is the HasMap object we use the follo0wing code for connection here ChatImpl is the stub

try
    {
        InetAddress Address = InetAddress.getLocalHost();
        ChatImpl csi = new ChatImpl(this);
        Naming.rebind("rmi://"+Address.getHostAddress()+":1099/ChatService", csi);
    }
public ArrayList getClientList()
{
    ArrayList myUser = new ArrayList();

    Iterator i = connectedUser.keySet().iterator();
    String user = null;

    while(i.hasNext())
    {
        user = i.next().toString();
        myUser.add(user);
    }

    return myUser;
}

public void addClient(Socket clientSocket) throws RemoteException
{
    connectedUser.put(getUsername(), clientSocket);
    sendPublicMessage(ONLINE, getUsername(), "CLIENT");
}

this is the client side code for array list

public void updateClient(ArrayList allClientList) throws RemoteException
{
    listClient.clear();
    int i = 0;
    String username;

    for(i=0; i<allClientList.size(); i++)
    {
        username = allClientList.get(i).toString();
        listClient.addElement(username);
    }
}