how to start @Schedule method in Java EJB

I have a Java Servlet. When the Servlet is called I would like to execute a command and call a method, that uses a Scheduler.

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Scheduler s = new Scheduler();
        s.doStuff();

.

 package xy;
 import javax.ejb.Schedule;
 import javax.ejb.Singleton;

  @Singleton
  public class Scheduler {

    private int counter = 0;

    @Schedule(second = "*/5", minute = "*", hour = "*", info="Every 5 seconds")
    public void  doStuff(){
        counter++;
        System.out.println("counter: " +counter);           
    }
}

Following my logic, every 5 seconds I should see a counter println getting higher and higher. But nothing happens.