public class Test {

    public static String test = "Hallo, ich bin eine Test Nachricht!";

    public static void main( String[] args ) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, InvalidAlgorithmParameterException {
        byte[] initVector = new byte[16];
        new Random().nextBytes( initVector );
        IvParameterSpec ivParameterSpec = new IvParameterSpec( initVector );
        KeyGenerator keyGenerator = KeyGenerator.getInstance( "AES" );
        SecretKey key = keyGenerator.generateKey();
        Cipher cipher = Cipher.getInstance( "AES/CBC/PKCS5PADDING" );

        cipher.init( Cipher.ENCRYPT_MODE, key, ivParameterSpec );
        byte[] toEncrypt = test.getBytes();
        byte[] encrypted = new byte[0];
        for ( int i = 0; i < toEncrypt.length; i++ ) {
            byte b = toEncrypt[i];
            byte[] result = cipher.update( new byte[]{ b } );
            encrypted = ArrayUtils.concatByteArrays( encrypted, result );
        }
        byte[] finalEncryptResult = cipher.doFinal();
        encrypted = ArrayUtils.concatByteArrays( encrypted, finalEncryptResult );

        cipher.init( Cipher.DECRYPT_MODE, key, ivParameterSpec );
        byte[] decrypted = new byte[0];
        for ( int i = 0; i < encrypted.length; i++ ) {
            byte b = encrypted[i];
            byte[] result = cipher.update( new byte[]{ b } );
            decrypted = ArrayUtils.concatByteArrays( decrypted, result );
        }
        byte[] finalDecryptResult = cipher.doFinal();
        decrypted = ArrayUtils.concatByteArrays( decrypted, finalDecryptResult );

        String decryptedText = new String( decrypted );
        System.out.println( test );
        System.out.println( decryptedText );
    }
}