code: private boolean hasContainerPageDefaultFile(CmsResource folder) {
  
          try {
              CmsResource defaultFile = A_CmsUI.getCmsObject().readDefaultFile(
                  folder,
                  CmsResourceFilter.ONLY_VISIBLE_NO_DELETED);
              return (defaultFile != null) && CmsResourceTypeXmlContainerPage.isContainerPage(defaultFile);
          } catch (CmsSecurityException e) {
              return false;
          }
      }
docs: Checks whether the folder has a default file of the type container page.<p>
  
  @param folder the folder to check
  
  @return <code>true</code> if the folder has a default file of the type container page