public MultipleSensorsEventsReader(List<SensorState> sensors) {
   eof = true;
   for (SensorState s : sensors) {
     EventsReader reader = new SingleSensorEventsReader(s);
     readers.add(reader);
     EventStorage.Event event = reader.next();
     if (event != null) eof = false;
     events.add(event);
   }
 }
 @Override
 public void close() {
   for (EventsReader r : readers) r.close();
 }