code: private static Collection<? extends URL> doFindPathMatchingFileResources(final URL rootDirResource, final String subPattern) {
  
          File rootFile = null;
          final Set<URL> rets = new LinkedHashSet<URL>();
  
          try {
              rootFile = new File(rootDirResource.toURI());
          } catch (final URISyntaxException e) {
              LOGGER.log(Level.ERROR, "cat not resolve the rootFile", e);
              throw new RuntimeException("cat not resolve the rootFile", e);
          }
          String fullPattern = StringUtils.replace(rootFile.getAbsolutePath(), File.separator, "/");
  
          if (!subPattern.startsWith("/")) {
              fullPattern += "/";
          }
          final String filePattern = fullPattern + StringUtils.replace(subPattern, File.separator, "/");
  
          @SuppressWarnings("unchecked") final Collection<File> files = FileUtils.listFiles(rootFile, new IOFileFilter() {
              @Override
              public boolean accept(final File dir, final String name) {
                  return true;
              }
  
              @Override
              public boolean accept(final File file) {
  
                  if (file.isDirectory()) {
                      return false;
                  }
                  if (AntPathMatcher.match(filePattern, StringUtils.replace(file.getAbsolutePath(), File.separator, "/"))) {
                      return true;
                  }
                  return false;
              }
          }, TrueFileFilter.INSTANCE);
  
          try {
              for (File file : files) {
                  rets.add(file.toURI().toURL());
              }
          } catch (final Exception e) {
              LOGGER.log(Level.ERROR, "convert file to URL error", e);
              throw new RuntimeException("convert file to URL error", e);
          }
  
          return rets;
      }
docs: scan the system file to get the URLS of the Classes.
  
  @param rootDirResource rootDirResource which is in File System
  @param subPattern      subPattern
  @return the URLs of all the matched classes