code: @Override
      public boolean isExtension() {
          if (isExtension == null) {
              if (archive.getType() == ArchiveType.ON_DEMAND_LIB) {
                  isExtension = false;
              } else {
                  Set<String> extensionClazz = archive.getExtensionClasses();
                  isExtension = extensionClazz.isEmpty() ? false : true;
              }
          }
          return isExtension;
      }
docs: Check whether the archive is an extension (application or runtime) or not
  
  @return