code: private boolean isOnlyFolders(String types) {
  
          boolean result = true;
          for (String type : types.split("[, ]+")) {
              try {
                  if (!OpenCms.getResourceManager().getResourceType(type).isFolder()) {
                      result = false;
                      break;
                  }
              } catch (CmsLoaderException e) {
                  // ignore
              }
          }
          return result;
      }
docs: Checks whether the given type list contains only folder types.<p>
  
  @param types the type list
  
  @return <code>true</code> if the given type list contains only folder types