QueueModel.java

import java.util.*;

public class QueueModel {

    public static void main(String[] args) {
        Queue<String> queue = new LinkedList<>();
        QueueMessageProducer producer = new QueueMessageProducer(queue);

        List<QueueConsumer> consumers = new ArrayList<>();

        for (int i = 0; i < 3; i++ ) {
            QueueConsumer consumer = new QueueConsumer(
                    "Consumer"  + i,
                    queue
            );
            consumer.start();

            consumers.add(consumer);
        }

        Scanner scanner = new Scanner(System.in);

        while(true) {
            String message = scanner.nextLine();
            producer.notify(message);
        }
    }

    static class QueueMessageProducer {

        private Queue<String> queue;

        public QueueMessageProducer(Queue<String> queue) {
            this.queue = queue;
        }

        public void notify(String message) {
            synchronized (queue) {
                queue.add(message);
                queue.notify();
            }
        }

    }

    static class QueueConsumer extends Thread {

        private Queue<String> queue;

        public QueueConsumer(String name, Queue<String> queue) {
            super(name);
            this.queue = queue;
        }

        @Override
        public void run() {
            try {
                while (true) {
                    synchronized (queue) {
                        queue.wait();
                    }

                    synchronized (queue) {
                        if (!queue.isEmpty()) {
                            String message = queue.poll();
                            System.out.printf(
                                    "%s: Consuming message: %s%n", getName(), message
                            );
                        }
                    }
                }
            } catch (Exception e) {
                System.out.printf(
                        "Exception occured: %s%n", e.toString()
                );
            }
        }

    }
}