code: public long getNumberOfEventsInTimeslot() {
  
  		final double thresholdTime = System.currentTimeMillis() - (timeslotInMilliseconds);
  		
  		return events.stream()
  				.filter(e -> e >= thresholdTime)
  				.count();
  	}
docs: Get the number of events in the timeslot
  @param thresholdTime
  @return