import java.util.LinkedList;

import java.util.Queue;

import java.util.Random;

/**

 * Simple Java program to demonstrate How to use wait, notify and notifyAll()

 * method in Java by solving producer consumer problem.

 *

 * @author Javin Paul

 */

public class ProducerConsumerInJava {

    public static void main(String args[]) {

        System.out.println("How to use wait and notify method in Java");

        System.out.println("Solving Producer Consumper Problem");

        Queue<Integer>  buffer = new LinkedList<>();

        int maxSize = 10;

        Thread producer = new Producer(buffer, maxSize, "PRODUCER");

        Thread consumer = new Consumer(buffer, maxSize, "CONSUMER");

        producer.start();

        consumer.start();

    }

    /**

     * Producer Thread will keep producing values for Consumer

     * to consumer. It will use wait() method when Queue is full

     * and use notify() method to send notification to Consumer

     * Thread.

     *

     * @author WINDOWS 8

     */

    static class Producer extends Thread {

        private Queue<Integer> queue;

        private int maxSize;

        public Producer(Queue<Integer> queue, int maxSize, String name) {

            super(name);

            this.queue = queue;

            this.maxSize = maxSize;

        }

        @Override

        public void run() {

            while (true) {

                synchronized (queue) {

                    while (queue.size() == maxSize) {

                        try {

                            System.out.println("Queue is full, " + "Producer thread waiting for " + "consumer to take something from queue");

                            queue.wait();

                        } catch (Exception ex) {

                            ex.printStackTrace();

                        }

                    }

                    Random random = new Random();

                    int i = random.nextInt();

                    System.out.println("Producing value : " + i);

                    queue.add(i);

                    queue.notifyAll();

                }

            }

        }

    }

    /**

     * Consumer Thread will consumer values form shared queue.

     * It will also use wait() method to wait if queue is

     * empty. It will also use notify method to send

     * notification to producer thread after consuming values

     * from queue.

     *

     * @author WINDOWS 8

     *

     */

    static class Consumer extends Thread {

        private Queue<Integer> queue;

        private int maxSize;

        public Consumer(Queue<Integer> queue, int maxSize, String name) {

            super(name);

            this.queue = queue;

            this.maxSize = maxSize;

        }

        @Override

        public void run() {

            while (true) {

                synchronized (queue) {

                    while (queue.isEmpty()) {

                        System.out.println("Queue is empty," + "Consumer thread is waiting" + " for producer thread to put something in queue");

                        try {

                            queue.wait();

                        } catch (Exception ex) {

                            ex.printStackTrace();

                        }

                    }

                    System.out.println("Consuming value : " + queue.remove());

                    queue.notifyAll();

                }

            }

        }

    }

}