code: private void addIntervalPattern(MethodSpec.Builder method, List<Node> pattern, String which) {
      for (Node node : pattern) {
        if (node instanceof Text) {
          method.addStatement("b.append($S)", ((Text)node).text());
        } else if (node instanceof Field) {
          Field field = (Field)node;
          method.addStatement("formatField($L, '$L', $L, b)", which, field.ch(), field.width());
        }
      }
    }
docs: Adds code to format a date time interval pattern, which may be the start or end
  date time, signified by the 'which' parameter.