import java.util.*;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

// Program som viser at vranglas (deadlock) kan oppst?.
// Skrevet av Stein Gjessing 2017 - 2025
// Refaktorert versjon

class Bil implements Runnable {
   private Veistump enVei, toVei;
   private int ind;
   public Bil (Veistump en, Veistump to, int i) {
        enVei = en;  toVei = to;
        ind = i;
   }
   public void run() {
        System.out.println(" Bil nr " + ind +
          " venter p? ? passere "+ enVei.del +" veistykke");
        enVei.taVei();
        // Det tar litt tid ? kj?re dette veistykket:
        try {Thread.sleep(10);}
           catch (InterruptedException e)
             {System.out.println("FEIL1"); System.exit(1);}
        System.out.println(" Bil nr " + ind +
          " venter p? ? passere "+ toVei.del +" veistykke");
        toVei.taVei();
        enVei.friVei();
        // Det tar litt tid ? kj?re dette veistykket:
        try {Thread.sleep(10);}
           catch (InterruptedException e)
            {System.out.println("FEIL2"); System.exit(1);}
        toVei.friVei();
        System.out.println(" Bil nr " + ind +
               " har passert hele den smale veien ");
        System.out.println();
    }
}
class Veistump  {
   private Lock l?s = new ReentrantLock();
   private Condition ledig = l?s.newCondition();
   private boolean veiLedig = true;
   final String del;
   public Veistump (String hvilken) {
       del = hvilken;
   }
   public void taVei() {
       l?s.lock();
       try {
           while (!veiLedig) {ledig.await();}
           // N? er veien ledig , den er min
           veiLedig = false;
        }
        catch (InterruptedException e)
            {System.out.println("FEIL3"); System.exit(1);}
        finally {l?s.unlock();}
    }
    public void friVei() {
        l?s.lock();
        try{
           veiLedig= true;
           ledig.signalAll();
        }
        finally {l?s.unlock();}
  }
}
class SmaltVeistykkeV2 {
   public static void main (String[] args) {
      Random ran = new Random();
      Scanner inn = new Scanner(System.in);
      System.out.println(" ");
      System.out.println(" Main starter ");
      Veistump venstre = new Veistump(" venstre " );
      Veistump hoyre   = new Veistump(" h?yre ");
      for (int ind = 1; ind <= 20; ind ++) {
          try {Thread.sleep((int)(ran.nextFloat()*1000));}
             catch (InterruptedException e)
               {System.out.println("FEIL4"); System.exit(1);}
          Bil  bilen1 = new Bil(venstre,hoyre,ind*2-1);
          new Thread(bilen1).start();
          try {Thread.sleep((int)(ran.nextFloat()*1000));}
             catch (InterruptedException e)
               {System.out.println("FEIL5"); System.exit(1);}
          Bil  bilen2 = new Bil(hoyre,venstre, ind*2);
          new Thread(bilen2).start();
      }
      System.out.println(" 40 biler er startet ");
      System.out.println(" Main er ferdig ");
  }
}