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

public class BrusEksempel {

    public static void main(String[] args) {

        int antallKjopere = 3;
        int brusPerPers = 5;
        int kapasitet = 5;
        int antallPaafyll = (antallKjopere * brusPerPers)/ kapasitet;

        BrusMaskin maskin = new BrusMaskin(kapasitet);

        // lager kjopere
        Runnable kjopBrus = new KjopBrus(maskin, brusPerPers);
        for (int i = 0; i < antallKjopere; i++) {
            Thread kjoper = new Thread(kjopBrus);
            kjoper.start();
        }

        // lager brusfyller
        Runnable fyllBrus = new FyllBrus(maskin, antallPaafyll);
        Thread fyller = new Thread(fyllBrus);
        fyller.start();

    }

}


class BrusMaskin {
    // Brusmaskinen er en monitor
    private final Lock brusLaas = new ReentrantLock();
    private final Condition harBrusTilSalgs = brusLaas.newCondition();
    private final Condition trengerPaafyll = brusLaas.newCondition();
    private final int kapasitet;
    private int brusTeller;

    public BrusMaskin(int kapasitet) {
        this.kapasitet = kapasitet;
        brusTeller = 0;
    }

    public void kjopBrus() {
        brusLaas.lock();
        try {
            while(brusTeller == 0) {
                harBrusTilSalgs.await();
            }
            System.out.println("Kjoper brus, antall igjen er " + --brusTeller);
            if (brusTeller == 0) {
                System.out.println("Maskinen trenger paafyll");
                trengerPaafyll.signal();
            }
        } catch (InterruptedException e) {
            System.out.println("Avbrutt under bruskjop");
        } finally {
            brusLaas.unlock();
        }
    }

    public void fyllBrus()  {
      brusLaas.lock();
      try {
          while(brusTeller > 0) {
              trengerPaafyll.await();
          }
          brusTeller = kapasitet;
          System.out.printf("Maskinen er fylt opp. Det er %d brus i maskinen%n", brusTeller);
          harBrusTilSalgs.signalAll();
      } catch (InterruptedException e) {
          System.out.println("Avbrutt under paafyll");
      } finally {
          brusLaas.unlock();
      }
    }

} // slutt BrusMaskin-klasse


class KjopBrus implements Runnable {

    private BrusMaskin maskin;
    private int antallKjop;


    public KjopBrus(BrusMaskin maskin, int antallKjop) {
        this.maskin = maskin;
        this.antallKjop = antallKjop;
    }


    public void run() {
        for (int i = 0; i < antallKjop; i++) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {}
            maskin.kjopBrus();
        }
    }
} // slutt KjopBrus-klasse


class FyllBrus implements Runnable {

    private BrusMaskin maskin;
    private int antallPaafyll;


    public FyllBrus(BrusMaskin maskin, int antallPaafyll) {
        this.maskin = maskin;
        this.antallPaafyll = antallPaafyll;
    }


    public void run() {
        for (int i = 0; i < antallPaafyll; i++) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {}
            maskin.fyllBrus();
        }
    }

} // slutt FyllBrus-klasse