Semaphore Sample

SemaphorePersonThread.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

public class SemaphorePersonThread extends Thread {
    Semaphore position;
    private int id;

    public SemaphorePersonThread(int i, Semaphore s) {
        this.id = i;
        this.position = s;
    }

    public void run() {
        try {
            if (position.availablePermits() > 0) {
                System.out.println("Person[" + this.id + "] in, seems has slots");
            } else {
                System.out.println("Person[" + this.id + "] in, seems NO slots");
            }
            position.acquire();
            System.out.println("Person[" + this.id + "] using");
            Thread.sleep((int) (10 + Math.random() * 800));
            System.out.println("Person[" + this.id + "] complete using");
            position.release();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]) {
        ExecutorService list = Executors.newCachedThreadPool();
        Semaphore position = new Semaphore(2);
        for (int i = 0; i < 10; i++) {
            list.submit(new SemaphorePersonThread(i + 1, position));
        }
        list.shutdown();
        position.acquireUninterruptibly(2);
        System.out.println("Everybody has been satisfied");
        position.release(2);
    }
}

One of possible output:

Person[2] in, seems has slots
Person[2] using
Person[6] in, seems has slots
Person[6] using
Person[3] in, seems has slots
Person[5] in, seems has slots
Person[4] in, seems has slots
Person[1] in, seems has slots
Person[7] in, seems NO slots
Person[8] in, seems NO slots
Person[9] in, seems NO slots
Person[10] in, seems NO slots
Person[2] complete using
Person[3] using
Person[6] complete using
Person[5] using
Person[5] complete using
Person[4] using
Person[3] complete using
Person[1] using
Person[4] complete using
Person[7] using
Person[7] complete using
Person[8] using
Person[1] complete using
Person[9] using
Person[8] complete using
Person[10] using
Person[10] complete using
Person[9] complete using
Everybody has been satisfied