public static String Szyfr(String plainText) {
        int shiftKey = 1;
        plainText = plainText.toLowerCase();
        String cipherText = "";
        for (int i = 0; i < plainText.length(); i += 2) {

            int charPosition = ALPHABET.indexOf(plainText.charAt(i));

            int keyVal = (shiftKey + charPosition) % 26;
            char replaceVal = ALPHABET.charAt(keyVal);
            cipherText = cipherText + new String(new char[]{replaceVal});

        }
        return cipherText;
    }