private static int parseEscapedBackSlash(@NotNull String str, int idx) {
    idx++;
    int len = str.length();
    if (idx >= len || str.charAt(idx) != 'u') return -1;
    do {
      idx++;
    }
    while (idx < len && str.charAt(idx) == 'u');
    if (idx + 3 >= len) return -1;
    try {
      int code = Integer.parseInt(str.substring(idx, idx + 4), 16);
      if (code == '\\') return idx + 4;
    }
    catch (NumberFormatException ignored) {
    }
    return -1;
  }
private static int parseEscapedBackSlash(@NotNull String str, int idx)