package examples;

import java.util.*;

/*
 * @author Kenneth J. Goldman, Washington University, kjg@wustl.edu
 * Created: Feb 22, 2005
 * 
 */
public class BlockingQueue<E> {
	private LinkedList<E> queue;
	int capacity;
	
	public BlockingQueue(int capacity) {
		this.capacity = capacity;
		queue = new LinkedList<E>();
	}

	public synchronized void enqueue(E x) {
		while (queue.size() >= capacity)
			try {
				System.out.println("waiting to enqueue " + x);
				wait();
			} catch (InterruptedException e) {
				// Do nothing.  Just go check the queue again.
			}
		queue.addLast(x);
		notifyAll();
	}

	public synchronized E dequeue() {
		while (queue.isEmpty())
			try {
				System.out.println("waiting to dequeue");
				wait();
			} catch (InterruptedException e) {
				// Do nothing.  Just go check the queue again.
			}
		E x = queue.removeFirst();
		notifyAll();
		return x;
	}
	
	public static void main(String[] args) {
		final BlockingQueue<Integer> q = new BlockingQueue<Integer>(3);
	
		class Producer extends Thread {
			int base;
			Producer(int base) { this.base = base; }
			public void run() {
				int i = 0;
				 while (i <= 50)
				 	  q.enqueue(base + i++);
			}			
		}
		
		class Consumer extends Thread {
			public void run() {
				int i = 0;
				 while (true) {
				 	  System.out.println("got " + (i = q.dequeue()));
				 }
			}		
		}
		
		Thread producer = new Producer(0);
		Thread producer2 = new Producer(100);		
		Thread consumer = new Consumer();

		producer.start();
		producer2.start();
		consumer.start();
	}
}




















/* SAMPLE OUTPUT WITH ONE CONSUMER AND ONE PRODUCER:
waiting to dequeue
waiting to enqueue 3
got 0
got 1
got 2
waiting to dequeue
waiting to enqueue 6
got 3
got 4
got 5
waiting to dequeue
waiting to enqueue 9
got 6
got 7
got 8
waiting to dequeue
waiting to enqueue 12
got 9
got 10
got 11
waiting to dequeue
waiting to enqueue 15
got 12
got 13
got 14
waiting to dequeue
waiting to enqueue 18
got 15
got 16
got 17
waiting to dequeue
waiting to enqueue 21
got 18
got 19
got 20
waiting to dequeue
waiting to enqueue 24
got 21
got 22
got 23
waiting to dequeue
waiting to enqueue 27
got 24
got 25
got 26
waiting to dequeue
waiting to enqueue 30
got 27
got 28
got 29
waiting to dequeue
waiting to enqueue 33
got 30
got 31
got 32
waiting to dequeue
waiting to enqueue 36
got 33
got 34
got 35
waiting to dequeue
waiting to enqueue 39
got 36
got 37
got 38
waiting to dequeue
waiting to enqueue 42
got 39
got 40
got 41
waiting to dequeue
waiting to enqueue 45
got 42
got 43
got 44
waiting to dequeue
waiting to enqueue 48
got 45
got 46
got 47
waiting to dequeue
got 48
got 49
got 50
*/