Manufacturing work cell - Software Development Case Studies in Java - page 213

public void subscribe(DiscreteProcess s, String event,
DiscreteProcess p) {
// Process "s" subscribes only to events activated
// after this subscription
subscriptions.add( new Subscription(s, event, p));
}
public void activate(DiscreteProcess p, String event,
long lifetime, Object obj){
// Publisher "p" activates "event" that will be raised
// after "lifeTime" seconds
eventQueue.add( new DiscreteEvent(event,
currentTime ! lifetime, p.name, obj));
Collections.sort(eventQueue);
}
public void next() {
// the GUI invokes this method to process the next event
while (eventQueue.size() > 0) {
DiscreteEvent mostRecentEvent #
(DiscreteEvent) eventQueue.remove(0);
currentTime # mostRecentEvent.raiseTime;
for ( int i # 0; i < subscriptions.size(); i !! )
((Subscription) subscriptions.get(i)).
notifyEvent(mostRecentEvent);
}
}
}
Class PieceSource implements the finite state machine of the inventory
system that loads raw pieces into the machines' input buffers. The current
version does not deal with the situation when the input buffers get full. It
generates new LOADED events at random time instants. The constructor
initializes the process name, the piece type and the loading rate, that is the
maximum number of pieces loaded per minute. The minimum rate is set to
half of the maximum rate. The actual rate is computed as a random number
between the minimum and maximum rate. An event's lifetime is computed
as the inverse of the actual loading rate.
package workcell;
public class PieceSource extends DiscreteProcess {
int numPieces # 0; // the total number of loaded pieces
String pieceType; // type of piece (nut or screw)
double maxRate; // max number of pieces per minute
// (in millisecs)
public PieceSource(String name, String type,
DiscreteClock clock, double rate) {
super (name, clock);
this .pieceType # type;