Как узнать число юзеров на сервере

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
public class SessionBindings extends HttpServlet implements Runnable{
 
 Set users = Collections.synchronizedSet(new HashSet());
Thread kick=null;
public void init(){
    kick= new Thread(this);
    kick.start();
        } 
public void run(){
    while(true){
 
        System.out.println('users inside : '+users.size());
        Iterator i=users.iterator();
        while(i.hasNext()){
            
            HttpSession tmp=(HttpSession)i.next();
            int sec=(int)(new Date().getTime()- tmp.getLastAccessedTime())/1000;
            System.out.println('last access '+sec);
            if (sec>250) i.remove();
            }
        try{kick.sleep(4000);}
        catch(Exception e){
            
            }
        }
    }       
public void doGet(HttpServletRequest req, HttpServletResponse res)
                        throws ServletException, IOException {
res.setContentType('text/plain');
PrintWriter out = res.getWriter();
 
HttpSession session = req.getSession(true);
 
session.setAttribute('binding',new HttpSessionBindingListener(){
 
public void valueBound(HttpSessionBindingEvent event) {
users.add(event.getSession());  
}
public void valueUnbound(HttpSessionBindingEvent event) {
System.out.println('UNBOUND as '+ event.getSession().getId());
}
});
 
out.println('About Session');
}
 
}