code: protected Double getDoubleParam(String paramName, String errorMessage, Map<String, Object> mapToUse)
              throws IOException {
          Object o = mapToUse.get(paramName);
          if (o != null) {
              try {
                  return Double.parseDouble(o.toString());
              } catch (NumberFormatException ignored) {
              }
          }
          return getTypedParam(paramName, errorMessage, Double.class, mapToUse);
      }
docs: Convenience method for subclasses. Retrieves a double with the given parametername, even if that
  parametercontent is actually a string containing a number or a long or an int or... Anything that
  can be converted to a double is returned.
  
  @param paramName    the name of the parameter
  @param errorMessage the errormessage to add to the exception if the param does not exist.
  @param mapToUse     an external hashmap to use as inputsource. Should not be null!
  @return a stringparameter with given name. If it does not exist and the errormessage is provided,
  an IOException is thrown with that message. if the errormessage is not provided, null is returned.
  @throws IOException Exception if the paramname does not exist and an errormessage is provided.