@Override
 public int hashCode() {
   final int prime = 31;
   int result = 1;
   result = prime * result + ((location == null) ? 0 : location.hashCode());
   result = prime * result + ((observationTime == null) ? 0 : observationTime.hashCode());
   result = prime * result + ((relativeHumidity == null) ? 0 : relativeHumidity.hashCode());
   result = prime * result + ((temperature == null) ? 0 : temperature.hashCode());
   result = prime * result + ((weatherDescription == null) ? 0 : weatherDescription.hashCode());
   result = prime * result + ((windDescription == null) ? 0 : windDescription.hashCode());
   result = prime * result + ((windDirection == null) ? 0 : windDirection.hashCode());
   return result;
 }