public static int dehexchar(char c) {
        if (c >= '0' && c <= '9') {
            return c - '0';
        }
        if (c >= 'A' && c <= 'F') {
            return c - ('A' - 10);
        }
        if (c >= 'a' && c <= 'f') {
            return c - ('a' - 10);
        }
        return -1;
    }