String token() {
            if (idx == null && val.getClass().isArray()) {
                int len = Array.getLength(val);
                StringBuilder b = new StringBuilder();
                for (int i = 0; i < len - 1; i++) {
                    b.append(token + "[" + i + "],");
                }
                b.append(token + "[" + (len - 1) + "]");
                return b.toString();
            }
            return token;
        }