/**
  * Returns the exchange of the given event or null.
  *
  * @param inEvent a <code>QuoteEvent</code> value
  * @return a <code>String</code> value
  */
 private static String getExchange(QuoteEvent inEvent) {
   if (inEvent != null) {
     return inEvent.getExchange();
   }
   return null;
 }