An example in java for Producer-Consumer problem using wait() and notify() :
/**
*
* @author vikky.agrawal
*/
public class Threads {
public static void main(String args[]) {
Semaphore mutex = new Semaphore();
Producer producer = new Producer(mutex);
Consumer consumer = new Consumer(mutex);
System.out.println("Main starts");
producer.start();
consumer.start();
try {
consumer.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Main Stop");
}
}
class Consumer extends Thread {
Semaphore mutex;
Consumer(Semaphore mutex) {
super("Consumer");
this.mutex = mutex;
}
@Override
public void run() {
for (int i = 0; i < 50; i++) {
try {
sleep(1000);
mutex.down();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class Producer extends Thread {
Semaphore mutex;
Producer(Semaphore mutex) {
super("producer");
this.mutex = mutex;
}
@Override
public void run() {
for (int i = 0; i < 100; i++) {
mutex.up();
try {
sleep(10);
} catch (InterruptedException e) {
}
}
}
}
class Semaphore {
static int value = 0;
boolean available = false;
public synchronized void down() {
while (!available) {
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
// System.out.println("Consumer woke up from waiting");
}
value--;
System.out.println("Consumed now value : " + value);
available = false;
notify();
}
public synchronized void up() {
while (available) {
try {
wait();
// System.out.println("Producer Got a notification and available is now: "+available);
} catch (InterruptedException e) {
e.printStackTrace();
}
// System.out.println("Producer woke up from waiting");
}
value++;
System.out.println("Produced now value :" + value);
available = true;
notify();
}
}
