import java.util.Vector;
/**
* Java program to solve Producer Consumer problem using wait and notify
* method in Java. Producer Consumer is also a popular concurrency design pattern.
*
* @author saurabhschool
*/
public class Main {
public static void main(String args[]) {
Vector sQueue = new Vector();
int size = 4; // vector can contain upto 5 elements
Thread producerThread = new Thread(new Producer(sQueue, size), "Producer");
Thread consumerThread = new Thread(new Consumer(sQueue, size, producerThread), "Consumer");
producerThread.start();
consumerThread.start();
}
}
class Producer implements Runnable {
private final Vector sQueue;
private final int SIZE;
public Producer(Vector sQueue, int size) {
this.sQueue = sQueue;
this.SIZE = size;
}
public void run() {
for (int i = 0; i < 12; i++) {
System.out.println("Producer trying to insert item: " + i);
try {
produce(i);
} catch (InterruptedException ex) {
System.out.println(ex);
}
}
}
private void produce(int i) throws InterruptedException {
//wait if queue is full
while (sQueue.size() == SIZE) {
synchronized (sQueue) {
System.out.println("Queue is full " + Thread.currentThread().
+ " is waiting , size: " + (sQueue.size()+1));
sQueue.wait();
}
}
//producing element and notify consumers
synchronized (sQueue) {
sQueue.add(i);
sQueue.notifyAll();
}
}
}
class Consumer implements Runnable {
private final Vector sQueue;
private final int SIZE;
private final Thread producerThread;
public Consumer(Vector sQueue, int size, Thread producerThread) {
this.sQueue = sQueue;
this.SIZE = size;
this.producerThread= producerThread;
}
public void run() {
while (true) {
try {
System.out.println("Consuming element: " );
if (consume()==-1) break;
Thread.sleep(50);
} catch (InterruptedException ex) {
System.out.println(ex);
}
}
}
private int consume() throws InterruptedException {
//wait if queue is empty
while (sQueue.isEmpty() ) {
// if producer thread has completed then return
if (!producerThread.isAlive())
return (-1);
synchronized (sQueue) {
System.out.println("Queue is empty " + Thread.currentThread().
+ " is waiting for new element inserted by a producer, size: " + sQueue.size());
sQueue.wait();
}
}
//Otherwise consume element and notify waiting producer
synchronized (sQueue) {
sQueue.notifyAll();
return (Integer) sQueue.remove(0);
}
}
}
