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
 *
 */
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
 *
 */
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();
            }
        }
    }
}

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