我想在这个加密器的字母表中添加字母“ç”、“ğ”、“ı”、“ö”和“ü”,也许还可以添加特殊字符。我怎样才能做到这一点?
    for (int i = 0; i < metin.length(); i++) {
        char harf = metin.charAt(i);
        if       (harf >= 'a' && harf <= 'm') harf += i;
        else if  (harf >= 'A' && harf <= 'M') harf += i;
        else if  (harf >= 'n' && harf <= 'z') harf -= i;
        else if  (harf >= 'N' && harf <= 'Z') harf -= i;
        System.out.print(harf);
    }