code: public static List<File> getMatchingFiles(String root, String filterExpr) {
          if (root == null)
              return Collections.emptyList();
  
          File file = new File(root);
          return getMatchingFiles(file, filterExpr);
      }
docs: Get a list of Files from the given path that match the provided filter;
  not recursive.
  
  @param root
  base directory to look for files
  @param filterExpr
  the regular expression to match, may be null
  @return List of File objects; List will be empty if root is null