public void removeSubscriber(Subscriber s)
    throws RemoteException;

  public void removeAllSubscribers()
    throws RemoteException;
}
 

public interface Subscriber extends Remote {
  public void update(Object pub, Object code)
    throws RemoteException;
}

Listing 2.
public class BasicPublisher implements Publisher {
  protected Vector subscribers = new Vector(2);

  public void addSubscriber(Subscriber s) {
    subscribers.addElement(s);
  }

  public void removeSubscriber(Subscriber s) {
    subscribers.removeElement(s);
  }

  public void removeAllSubscribers() {
    subscribers.removeAllElements();
  }

  public void notifySubscribers(Object pub, Object code) {
    Vector deadSubs = null;
    Enumeration e = subscribers.elements();
    while (e.hasMoreElements()) {
      Subscriber s = (Subscriber) e.nextElement();
      try { s.update(pub, code); }
      catch (java.rmi.ConnectException ce) { //serious
        if (deadSubs == null) deadSubs = new Vector();
        deadSubs.addElement(s);// must be dead
      }
      catch (java.rmi.NoSuchObjectException nsoe){ //serious
        if (deadSubs == null) deadSubs = new Vector();
        deadSubs.addElement(s);// must be dead
      }
      catch (java.rmi.RemoteException re) {
        /*might recover?*/
      }
    }
    if (deadSubs != null) {
      e = deadSubs.elements();
      while (e.hasMoreElements()) {
        Subscriber s = (Subscriber) e.nextElement();
        removeSubscriber(s);  // forget this subscriber
      }
    }
  }

  public void notifySubscribers(Object pub) {
    notifySubscribers(pub, null);
  }
}

Listing 3.

public class XX implements Publisher {
  BasicPublisher pub = new BasicPublisher();

  /** Delegate Publisher interface to BasicPublisher */
  public void addSubscriber(Subscriber s) {
    pub.addSubscriber(s);
  }
  public void removeSubscriber(Subscriber s) {
    pub.removeSubscriber(s);
  }
  public void removeAllSubscribers() {
    pub.removeAllSubscribers();
  }
  ...
  ...
}