code: private Set<String> findResourceNamesFromFileSystem(String classPathRootOnDisk, String scanRootLocation, File folder) {
          LOGGER.debug("Scanning for resources in path: {} ({})", folder.getPath(), scanRootLocation);
  
          File[] files = folder.listFiles();
          if (files == null) {
              return emptySet();
          }
  
          Set<String> resourceNames = new TreeSet<>();
  
          for (File file : files) {
              if (file.canRead()) {
                  if (file.isDirectory()) {
                      resourceNames.addAll(findResourceNamesFromFileSystem(classPathRootOnDisk, scanRootLocation, file));
                  } else {
                      resourceNames.add(toResourceNameOnClasspath(classPathRootOnDisk, file));
                  }
              }
          }
  
          return resourceNames;
      }
docs: Finds all the resource names contained in this file system folder.
  
  @param classPathRootOnDisk The location of the classpath root on disk, with a trailing slash.
  @param scanRootLocation    The root location of the scan on the classpath, without leading or trailing slashes.
  @param folder              The folder to look for resources under on disk.
  @return The resource names;