public static double getRequiredDouble(final Element element, final String attributeName) {
    final String str = getRequiredString(element, attributeName);
    try {
      return Double.parseDouble(str);
    }
    catch (NumberFormatException e) {
      throw new IllegalArgumentException("attribute '" + attributeName + "' is not a proper double: " + str);
    }
  }
public static double getRequiredDouble(final Element element, final String attributeName)