package com.codepumpkin.concurrency.producerConsumer;

import java.util.LinkedList;
import java.util.Queue;
import java.util.Random;


/**
 * Simple Java Program to test Producer Consumer Design Pattern 
 * using  wait, notify and notifyAll() methods 
 *
 * @author CodePumpkin
 *
 */
public class ProducerConsumerTest {

	public static void main(String[] args) throws InterruptedException {
		
		
		final Queue sharedQ = new LinkedList<Integer>();
		
		Thread consumerThread = new Thread(new Consumer(sharedQ, 4), "CONSUMER");
		Thread producerThread = new Thread(new Producer(sharedQ, 4), "PRODUCER");
		
		producerThread.start();
		consumerThread.start();
		
		producerThread.join();
		
	}

}

/**
 * Producer Thread will keep producing values for Consumer.
 * 
 * It will use wait() method when Queue is full and 
 * use notify() method to send notification to Consumer Thread.
 * 
 * @author CodePumpkin
 *
 */
class Producer implements Runnable
{
	private final Queue sharedQ;
	private int maxSize;
	
	public Producer(Queue sharedQ, int maxSize)
	{
		this.sharedQ = sharedQ;
		this.maxSize = maxSize;
	}
	
	@Override
	public void run(){
		
		while(true)
		{
			synchronized (sharedQ) {
				while(sharedQ.size()==maxSize)
				{
					try
					{
						System.out.println("Queue is full");
						sharedQ.wait();
					}
					catch(InterruptedException e)
					{
						e.printStackTrace();
					}
					
				}
				Random random = new Random(); 
				int number = random.nextInt(100);
				System.out.println("Producing value " + number);
				sharedQ.add(number);
				sharedQ.notify();
				
			}
			
		}
	}
}

/**
 * Consumer Thread will consumer values form shared queue. 
 * 
 * It will 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 CodePumpkin
 *
 */
class Consumer implements Runnable
{
	private final Queue sharedQ;
	private int maxSize;
	
	public Consumer(Queue sharedQ, int maxSize)
	{
		this.sharedQ = sharedQ;
		this.maxSize = maxSize;
	}
	
	@Override
	public void run(){
		while(true)
		{
			synchronized (sharedQ) {
				while(sharedQ.isEmpty())
				{
					try {
						System.out.println("Que is Empty");
						sharedQ.wait();
					}
					catch(InterruptedException e)
					{
						e.printStackTrace(); 
					}
				}
				
				int number = (int) sharedQ.poll();
				System.out.println("removing Element " + number);
				sharedQ.notify();
				
			}
		}
	}
	
}