package multithreading;

import java.util.concurrent.*;

class Shared {

static int count = 0 ;

}

public class SemaphoreMethod extends Thread {

Semaphore sem;

String threadName;

public SemaphoreMethod(Semaphore sem, String threadName) {

super(threadName);

this.sem = sem;

this.threadName = threadName;

}

@Override

public void run() {

// run by thread A

if(this.getName().equals("A")) {

System.out.println("Starting " + threadName);

try {

System.out.println(threadName + " is waiting for a permit.");

// acquiring the lock

sem.acquire();

System.out.println(threadName + " gets a permit.");

for(int i = 0; i < 5; i++) {

Shared.count++;

System.out.println(threadName + ": " + Shared.count);

Thread.sleep(100);

}

} catch (Exception e) {

System.out.println("Exception: "+e);

}

System.out.println(threadName + " releases the permit.");

sem.release();

} else { // run by thread B

System.out.println("String " + threadName);

try {

System.out.println(threadName + " is waiting for a permit");

sem.acquire();

System.out.println(threadName + " gets a permit");

for(int i = 0; i < 5; i++) {

Shared.count--;

System.out.println(threadName + ": " + Shared.count);

Thread.sleep(100);

}

} catch (Exception e) {

System.out.println("Exception: " +e);

}

}

}

public static void main(String[] args) throws InterruptedException {

Semaphore sem = new Semaphore(1);

SemaphoreMethod mt1 = new SemaphoreMethod(sem, "A");

SemaphoreMethod mt2 = new SemaphoreMethod(sem, "B");

// stating threads A and B

mt1.start();

mt2.start();

// waiting for threads A and B

mt1.join();

mt2.join();

System.out.println("Count: " + Shared.count);

}

}