public static Optional<String> generateKey() {
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance(ALGORITHM);
            keyGenerator.init(SIZE);
            SecretKey secretKey = keyGenerator.generateKey();
            String keys = new String(Base64.getEncoder().encode(secretKey.getEncoded()), DEFAULT_ENCODE);
            return Optional.of(keys);
        } catch (IOException | GeneralSecurityException e) {
            return Optional.empty();
        }
    }
@Test
    void generateKey() {
        Optional<String> optional = AesUtil.generateKey();
        Assertions.assertTrue(optional.isPresent());
    }