code: public static Set<Path> getDirectoriesFromJar(Path pathToJarFile) throws IOException {
          Set<Path> result = new HashSet<Path>();
          ZipFile jarfile = new ZipFile(pathToJarFile.toFile());
          try {
              final Enumeration<? extends ZipEntry> entries = jarfile.entries();
              while (entries.hasMoreElements()) {
                  ZipEntry entry = entries.nextElement();
                  if (entry.isDirectory()) {
                      result.add(Paths.get(entry.getName()));
                  }
              }
              jarfile.close();
          } finally {
              IOUtils.closeQuietly(jarfile);
          }
          return result;
      }
docs: Get all of the directory paths in a zip/jar file
  @param pathToJarFile location of the jarfile. can also be a zipfile
  @return set of directory paths relative to the root of the jar