package geneticAnt;

// Classical Semaphores in Java, I hope

public class Semaphore {

      private int n;  // the counter 
      // For debugging:
      private boolean debug = false; 
      private String name = "";
      private long    sem_num;    

      public  Semaphore() { n = 0; }
      public  Semaphore(int n)  { this.n = n; }
      public  Semaphore(int n, boolean debug, String name) { 
         this.n = n; 
         this.debug = debug;
         this.name = name;
         if (debug) {
            String who = Thread.currentThread().getName();
            sem_num = Math.round(Math.random()*100.00);
            System.out.println("In " + who + " Sem " + name + sem_num + 
            " is created. Init to " + n);
         }
     }

     public  Semaphore(int n, boolean debug) { 
         this(n, debug, "");
        
     }
    
      public synchronized void P() {
         String who = Thread.currentThread().getName();
         
         if (debug)
     System.out.println("In sem " + name + sem_num + ", " + who + " wants a resource");
         n--;
         if (n < 0)
            try {
              if (debug) System.out.println(who + " will wait");
       wait();
     }
     catch (InterruptedException e){} ;
     if (debug) System.out.println(who + " gets a resource");
      } 

  
     public synchronized void V() {
        String who = Thread.currentThread().getName(); 
       
        if (debug) 
     System.out.println("In sem " + name + sem_num + ", " + who + " releases a resource");
        n++;
        if (n <= 0 )
           if (debug) System.out.println("Sem " + name + sem_num + " is notifiying");
           notify();
      }

}