public class ProducerConsumer {

    class Producer {
        final Lagerhalle lagerhalle;

        Producer(final Lagerhalle lagerhalle) {
            this.lagerhalle = lagerhalle;
        }

        void produce() {
            int tmp = 0;
            while (!Thread.interrupted()) {
                try {
                    lagerhalle.add(tmp++);
                    System.out.println("produced " + tmp);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    class Consumer {
        final Lagerhalle lagerhalle;

        Consumer(final Lagerhalle lagerhalle) {
            this.lagerhalle = lagerhalle;
        }

        void consume() {
            while (!Thread.interrupted()) {
                try {
                    int tmp = lagerhalle.get();
                    System.out.println("consumed " + tmp);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    class Lagerhalle {
        private int[] elements = new int[10];
        private int used = 0;

        synchronized void add(int element) throws InterruptedException {
            while (used == elements.length - 1) {
                wait();
            }
            elements[used++] = element;
            notifyAll();
        }

        synchronized int get() throws InterruptedException {
            while (used == 0) {
                wait();
            }
            int tmp = elements[used-- - 1];
            notifyAll();
            return tmp;
        }
    }

    void start() {
        var lh = new Lagerhalle();
        new Thread(() -> new Producer(lh).produce()).start();
        new Thread(() -> new Consumer(lh).consume()).start();
    }

    public static void main(String... args) {
        var pc = new ProducerConsumer();
        pc.start();
    }
}