APPLICATION DES SEMAPHORE POUR LA RESOLUTION DU PROBLEME DES TRAINS

/**
 * Algorithme d'une sémaphore
 * 
 * @author YERMES MOHAMMED EL AMINE
 * 
 * UNIVERSITE DE MASCARA
 * @version 1.0 20/08/2008
 */


class Semaphore {

   protected int value = 0;

   protected Semaphore() {value = 1;}

   protected Semaphore(int valeur) {value = valeur;}


   public synchronized boolean occupe() { 
   	if (value>0) 	return false;
   	else		return true;
   }


  /* public synchronized void signaler() { 
   	value = value + 1;
   	notify();
   }

   public synchronized void initialise() { 
   	value = value - 1;
   }*/




   public synchronized void P() {
      value--;
      if (value < 0) {
         while (true) {  
            try {
               wait();
               break;      
            } catch (InterruptedException e) {
               System.err.println
                  ("Semaphore.P()");
               continue;
              }
         }
      }
   }

   public synchronized void V() { 
      value++;                    
      if (value <= 0) notify();
   }

   public synchronized int value() {
      return value;
   }

   public synchronized String toString() {
      return String.valueOf(value);
   }

}