@Contract(value = "null,!null,_ -> false; !null,null,_ -> false; null,null,_ -> true", pure = true)
  public static boolean equal(@Nullable CharSequence s1, @Nullable CharSequence s2, boolean caseSensitive) {
    return StringUtilRt.equal(s1, s2, caseSensitive);
  }
@Contract(value = "null,!null,_ -> false; !null,null,_ -> false; null,null,_ -> true", pure = true)
  public static boolean equal(@Nullable CharSequence s1, @Nullable CharSequence s2, boolean caseSensitive)