code: private static void checkEventType(String eventSetName,
              Method listenerMethod) throws IntrospectionException {
          Class<?>[] params = listenerMethod.getParameterTypes();
          String firstParamTypeName = null;
          String eventTypeName = prepareEventTypeName(eventSetName);
  
          if (params.length > 0) {
              firstParamTypeName = extractShortClassName(params[0]
                      .getName());
          }
  
          if (firstParamTypeName == null
                  || !firstParamTypeName.equals(eventTypeName)) {
              throw new IntrospectionException("Listener method " +
                      listenerMethod.getName() + " should have parameter of type " + eventTypeName);
          }
      }
docs: Checks that given listener method has an argument of the valid type.
  
  @param eventSetName
  event set name
  @param listenerMethod
  listener method
  @throws IntrospectionException
  if check fails