code: private static Collection<String> normalize(
        final Collection<String> rackNames) throws IllegalArgumentException {
  
      return normalize(rackNames, true);
    }
docs: Normalize rack names. Make sure that each rack name starts with a path separator /
  and does not have a path separator at the end. Also check that no rack names
  end with a wildcard *, and raise an exception if such rack name occurs in the input.
  @param rackNames Collection of rack names to normalize.
  @return Collection of normalized rack names.
  @throws IllegalArgumentException if validation of some rack names' fails.