code: private List<NumberPattern> getNumberPattern(String pattern) {
      int i = pattern.indexOf(';');
      if (i == -1) {
        return Arrays.asList(
            parseNumberPattern(pattern),
            parseNumberPattern("-" + pattern));
      }
      return Arrays.asList(
          parseNumberPattern(pattern.substring(0, i)),
          parseNumberPattern(pattern.substring(i+1)));
    }
docs: Return a pair of patterns (positive, negative) derived from the given pattern string.