import java.rmi.*;import java.rmi.server.*;public class CallBackImpl extends UnicastRemoteObject    implements CallBack {  // The client will be called by the server through callback  private TicTacToeClientRMI thisClient;  /** Constructor */  public CallBackImpl(Object client) throws RemoteException {    thisClient = (TicTacToeClientRMI)client;  }  /** The server notifies the client for taking a turn */  public void takeTurn(boolean turn) throws RemoteException {    thisClient.setMyTurn(turn);  }  /** The server sends a message to be displayed by the client */  public void notify(String message) throws RemoteException {    thisClient.setMessage(message);  }  /** The server notifies a client of the other player's move */  public void mark(int row, int column, char token)      throws RemoteException {    thisClient.mark(row, column, token);  }}