Car parking - Software Development Case Studies in Java - page 287

public void attachTo(EventProcess process) {
process.addObserver( this );
}
// notifies this process that "observable" raised "event"
public synchronized void update(Observable observable,
Object event) {
// records the name of the observable and of the event
// in member variable;
this .observable # observable.toString();
this .event # (String) event;
// wakes up the thread that is waiting for an event
notify();
}
// the waitEvent() method is invoked by an Observer
// object; it suspends this thread until process
// "p_observable" raises event "p_event"
public synchronized void waitEvent(Observable observable,
String event) {
// verifies that the event has been raised
while (! ( this .observable.equals(observable.toString()) &&
this .event.equals(event)))
try {
// the thread suspends its execution until the
// notify() method has been invoked
this .wait();
}
catch (InterruptedException ie)
{ ie.printStackTrace();}
// reset the event; this allows the process to wait for
// a new event of the same type
this .event # "";
}
// this method is called by an Observable object;
// it notifies the observers that its state has changed
public void notifyObservers(String event) {
this .setChanged();
super .notifyObservers(event);
}
// starts this process
public void start() {
// creates a thread object and starts it
thread # new Thread( this );
if (! alive) {
alive # true ;
thread.start();
}
}