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

class ConditionTest {
    public static void main(String[] args) {
        Monitortest monitor = new Monitortest();

        for (int i = 0; i < 1000; i++) {
            new Thread(new Fjerner(monitor)).start();
            new Thread(new Leggertil(monitor)).start();
        }
    }
}

class Fjerner implements Runnable {
    Monitortest monitor = new Monitortest();

    public Fjerner(Monitortest m){
        this.monitor = m;
    }

    @Override
    public void run() {
        try {
            monitor.fjern();
            System.out.println("fjernet");
        } catch (InterruptedException e) {
        }
    }
}

class Leggertil implements Runnable {
    Monitortest monitor = new Monitortest();

    public Leggertil(Monitortest m){
        this.monitor = m;
    }

    @Override
    public void run() {
        monitor.leggTil("x");
        System.out.println("la til");
    }

}

class Monitortest{
    ArrayList<String> beholder = new ArrayList<>();
    private final Lock laas = new ReentrantLock();
    Condition ikkeTom = laas.newCondition();

    public void leggTil(String s){
        laas.lock();

        try{
            beholder.add(s);
            ikkeTom.signalAll();
        }
        finally{
            laas.unlock();
        }
    }

    public void fjern() throws InterruptedException{
        laas.lock();

        try{
            while(hentSize()==0){
                ikkeTom.await();
            }

            beholder.remove(0);
        }
        finally{
            laas.unlock();
        }
    }

    public int hentSize(){
        laas.lock();

        try {
            return beholder.size();
        } 
        
        finally {
            laas.unlock();
        }

    }
}