public Restaurant(ExecutorService e, int nWaitPersons, int nChefs) {
   exec = e;
   for (int i = 0; i < nWaitPersons; i++) {
     WaitPerson waitPerson = new WaitPerson(this);
     waitPersons.add(waitPerson);
     exec.execute(waitPerson);
   }
   for (int i = 0; i < nChefs; i++) {
     Chef chef = new Chef(this);
     chefs.add(chef);
     exec.execute(chef);
   }
 }