code: private static void addEntry(ZipEntrySource entry, ZipOutputStream out) throws IOException {
      out.putNextEntry(entry.getEntry());
      InputStream in = entry.getInputStream();
      if (in != null) {
        try {
          IOUtils.copy(in, out);
        }
        finally {
          IOUtils.closeQuietly(in);
        }
      }
      out.closeEntry();
    }
docs: Adds a given ZIP entry to a ZIP file.
  
  @param entry
  new ZIP entry.
  @param out
  target ZIP stream.