@Contract(pure = true)
  public static int findFirst(@NotNull CharSequence s, @NotNull CharFilter filter) {
    for (int i = 0; i < s.length(); i++) {
      char ch = s.charAt(i);
      if (filter.accept(ch)) {
        return i;
      }
    }
    return -1;
  }
@Contract(pure = true)
  public static int findFirst(@NotNull CharSequence s, @NotNull CharFilter filter)