code: public static void packEntries(File[] filesToPack, File destZipFile, NameMapper mapper) {
      packEntries(filesToPack, destZipFile, mapper, DEFAULT_COMPRESSION_LEVEL);
    }
docs: Compresses the given files into a ZIP file.
  <p>
  The ZIP file must not be a directory and its parent directory must exist.
  
  @param filesToPack
  files that needs to be zipped.
  @param destZipFile
  ZIP file that will be created or overwritten.
  @param mapper
  call-back for renaming the entries.