//Java implementation of a producer and consumer
//that use semaphores to control synchronization
import java.util.concurrent.Semaphore;
class Queue {
// an item
int item;
// semCon initialized with 0 permits
// to ensure put() executes first
static Semaphore semCon = new Semaphore(0);
static Semaphore semProd = new Semaphore(1);

//to get an item from buffer
void get() {
try {
// Before consumer can consume an item,
// it must acquire a permit from semCon
semCon.acquire();
}
catch(InterruptedException e) {
System.out.println("InterruptedException caught");
}

//consumer consuming an item
System.out.println("Consumer consumed item : " + item);
// After consumer consumes the item,
// it releases semProd to notify producer
semProd.release();
}

//to put an item in buffer
void put(int item) {
try {
// Before producer can produce an item,
// it must acquire a permit from semProd
semProd.acquire();
} catch(InterruptedException e) {
System.out.println("InterruptedException caught");
}
//producer producing an item
this.item = item;
System.out.println("Producer produced item : " + item);
// After producer produces the item,
// it releases semCon to notify consumer
semCon.release();
}
}