public String get_username(int id) {
	   
	   if(users == null) return "";
	   List listusers = users.getChildren();
	   if (listusers != null){
		   Iterator i = listusers.iterator();
		   while(i.hasNext()){
			   Element current = (Element)i.next();
			   int currid = Integer.parseInt(current.getAttributeValue("id"));
			   if(currid == id) {
				   return current.getAttributeValue("name");
			   }
		   }
	   }
	   return "";
   }