PubSubModel.java

import java.util.*;
import java.util.Queue;

public class PubSubModel {

    public static void main(String[] args) {
        List<Consumer> consumers = new ArrayList<>();

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

            consumers.add(consumer);
        }

        Scanner scanner = new Scanner(System.in);

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

            for (Consumer consumer: consumers) {
                consumer.notify(message);
            }

        }
    }

    static class Consumer extends Thread {

        private Queue<String> queue;

        public Consumer(String name) {
            super(name);
            this.queue = new LinkedList<>();
        }

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

                    synchronized (queue) {
                        String message = queue.poll();

                        System.out.println(
                                getName() + ": Consuming message: " + message
                        );
                    }
                }
            } catch (Exception e) {
                System.out.printf(
                        "Exception occured: %s%n", e.toString()
                );
            }
        }

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

}