code: Double readMaxNavPos(CmsResource target) throws CmsException {
  
          List<CmsResource> existingResourcesInFolder = m_cms.readResources(
              target,
              CmsResourceFilter.IGNORE_EXPIRATION,
              false);
  
          double maxNavpos = 0.0;
          boolean hasNavpos = false;
          for (CmsResource existingResource : existingResourcesInFolder) {
              CmsProperty navpos = m_cms.readPropertyObject(
                  existingResource,
                  CmsPropertyDefinition.PROPERTY_NAVPOS,
                  false);
              if (navpos.getValue() != null) {
                  try {
                      double navposNum = Double.parseDouble(navpos.getValue());
                      hasNavpos = true;
                      maxNavpos = Math.max(navposNum, maxNavpos);
                  } catch (NumberFormatException e) {
                      // ignore
                  }
              }
          }
          if (hasNavpos) {
              return Double.valueOf(maxNavpos);
          } else {
              return null;
          }
      }
docs: Reads the max nav position from the contents of a folder.<p>
  
  @param target a folder
  @return the maximal NavPos from the contents of the folder, or null if no resources with a valid NavPos were found in the folder
  
  @throws CmsException if something goes wrong