code: public static void unpack(InputStream is, File outputDir, NameMapper mapper) {
      unpack(is, outputDir, mapper, null);
    }
docs: Unpacks a ZIP stream to the given directory.
  <p>
  The output directory must not be a file.
  
  @param is
  inputstream for ZIP file.
  @param outputDir
  output directory (created automatically if not found).
  @param mapper
  call-back for renaming the entries.