code: protected static double getPriority(List<CmsProperty> properties) {
  
          CmsProperty prop = CmsProperty.get(CmsPropertyDefinition.PROPERTY_XMLSITEMAP_PRIORITY, properties);
          if (prop.isNullProperty()) {
              return -1.0;
          }
          try {
              double result = Double.parseDouble(prop.getValue().trim());
              return result;
          } catch (NumberFormatException e) {
              return -1.0;
          }
      }
docs: Gets the page priority from a list of properties.<p>
  
  If the page priority can't be found among the properties, -1 will be returned.<p>
  
  @param properties the properties of a resource
  
  @return the page priority read from the properties, or -1