code: public static Double selectDouble(Node node,
                                        String xpath, Double defaultValue) {
          return selector.selectDouble(node, xpath, defaultValue);
      }
docs: Extract a double precision floating point value from {@code node} or
  return {@code defaultValue} if it is not found
  
  @param node         the node with the wanted attribute.
  @param xpath        the XPath to extract.
  @param defaultValue the default value.
  @return the value of the path, if existing, else
  defaultValue