code: DownloadableFileType getArchiveType() {
          try {
              return DownloadableFileType.valueOf(FilenameUtils.getExtension(decompressedFilename).toUpperCase());
          } catch (IllegalArgumentException e) {
              LOG.debug("Not a recognised Archive type");
              return null;
          }
      }
docs: Find out if the uncompressed file is an archive
  
  @return ArchiveType.TAR if a tar, or null if not an archive