code: static String [] searchJrtFSForClasses( URL url ) throws IOException {
          try {
              Path path = FileSystems.getFileSystem(new URI("jrt:/")).getPath("modules", url.getPath());
  
              return Files.walk(path).map(Path::toString)
                      .filter(BshClassPath::isClassFileName)
                      .map(BshClassPath::canonicalizeClassName)
                      .toArray(String[]::new);
          } catch (URISyntaxException e) { /* ignore */ }
          return new String[0];
      }
docs: Search jrt file system for module classes.
  @param the jrt: file system url
  @return array of class names found
  @throws IOException