Concurrency Utilities

[Singh Harmeet]

in concurrency utilities we use "Semaphore" how the semaphore work??
we assign the values of permit in "Semaphore(value) constructor, how the permit work???

How the semaphore work in this code???

// An implementation of a producer and consumer
// that use semaphores to control synchronization.

import java.util.concurrent.Semaphore;

class Q {
int n;

// Start with consumer semaphore unavailable.
static Semaphore semCon = new Semaphore(0);
static Semaphore semProd = new Semaphore(1);

void get() {
try {
semCon.acquire();
} catch(InterruptedException e) {
System.out.println("InterruptedException caught");
}

System.out.println("Got: " + n);
semProd.release();
}

void put(int n) {
try {
semProd.acquire();
} catch(InterruptedException e) {
System.out.println("InterruptedException caught");
}

this.n = n;
System.out.println("Put: " + n);
semCon.release();
}
}

class Producer implements Runnable {
Q q;

Producer(Q q) {
this.q = q;
new Thread(this, "Producer").start();
}

public void run() {
for(int i=0; i < 20; i++) q.put(i);
}
}

class Consumer implements Runnable {
Q q;

Consumer(Q q) {
this.q = q;
new Thread(this, "Consumer").start();
}

public void run() {
for(int i=0; i < 20; i++) q.get();
}
}

class ProdCon {
public static void main(String args[]) {
Q q = new Q();
new Consumer(q);
new Producer(q);
}
}

[asit dhal]

read this link
http://download.oracle.com/javase/1,5.0/docs/api/java/util/concurrent/Semaphore.html#Semaphore%28int%29

at least read the functions Semaphore(), release() and acquire()