code: private void checkStringIsValidName(final String s) throws PackageNameException {
          final boolean packageContainsJavaKeyword = javaKeywords.stream().anyMatch(s::equals);
          if (packageContainsJavaKeyword || s.matches("\\d.*")) {
              throw new PackageNameException("string is not valid");
          }
      }
docs: Checks that string is not java keyword and is qualified java name
  @param s to be checked
  @throws PackageNameException thrown when string passed is java keyword