Example for java.util.concurrent.Semaphore usage

Let's try to increment a simple integer variable without any synchronization.
See what happens if we don't care about critical sections :)

Yes even we are not able to increment an integer without using any synchronization primitives.So we see the values of "i" 10-11-10 which are highlighted in the messages pane of my ide.

And...Here is the succesfull result in which we are using a Semaphore from java 1.5 (Tiger).

import java.util.concurrent.locks.*;
import java.util.concurrent.Semaphore;

public class SemaphoreExample {
    int i = 0;

    public static void main (String[] args) {
        final SemaphoreExample example = new SemaphoreExample();
        final Semaphore semaphore = new Semaphore (1);

        final Runnable r = new Runnable () {
            public void run () {
                while (true) {
                    try {
                        semaphore.acquire();
                        example.printSomething ();
                        Thread.sleep (1000);
                        semaphore.release();
                    } catch (Exception ex) {
                        System.out.println (" -- Interrupted...");
                        ex.printStackTrace ();
                    }
                }
            }
        };

        new Thread (r).start ();
        new Thread (r).start ();
        new Thread (r).start ();
    }

    public void printSomething (){
        i++;
        System.out.println (" -- current value of the i :"+ i);
    }
}