docs: public void createDirectoryEntries(JarOutputStream jarStream, String packageName) throws IOException {
          StringBuilder entryName = new StringBuilder(packageName.length());
          for (String str : packageName.split("\\.")) {
              entryName.append(str).append("/");
              JarEntry jarEntry = new JarEntry(entryName.toString());
              jarStream.putNextEntry(jarEntry);
          }
      }