public void adjustTellerNumber() {
// This is actually a control system. By adjusting
// the numbers, you can reveal stability issues in
// the control mechanism.
// If line is too long, add another teller:
if (customers.size() / workingTellers.size() > 2) {
// If tellers are on break or doing
// another job, bring one back:
if (tellersDoingOtherThings.size() > 0) {
Teller teller = tellersDoingOtherThings.remove();
teller.serveCustomerLine();
workingTellers.offer(teller);
return;
}
// Else create (hire) a new teller
Teller teller = new Teller(customers);
exec.execute(teller);
workingTellers.add(teller);
return;
}
// If line is short enough, remove a teller:
if (workingTellers.size() > 1 && customers.size() / workingTellers.size() < 2)
reassignOneTeller();
// If there is no line, we only need one teller:
if (customers.size() == 0) while (workingTellers.size() > 1) reassignOneTeller();
}
public void run() {
try {
while (!Thread.interrupted()) {
TimeUnit.MILLISECONDS.sleep(adjustmentPeriod);
adjustTellerNumber();
System.out.print(customers + " { ");
for (Teller teller : workingTellers) System.out.print(teller.shortString() + " ");
System.out.println("}");
}
} catch (InterruptedException e) {
System.out.println(this + "interrupted");
}
System.out.println(this + "terminating");
}
// Give a teller a different job or a break:
private void reassignOneTeller() {
Teller teller = workingTellers.poll();
teller.doSomethingElse();
tellersDoingOtherThings.offer(teller);
}