public class MainActivity extends AppCompatActivity {

    private static final String PUBLIC_KEY_BASE64_ENCODED = "INSERT HERE";

    private final Gson gson = new Gson();

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

try {

            PayLoadRequest request = new PayLoadRequest(
                    "first field",
                    "TeknoSeyir"
            );

            System.out.println("-------------------------------------------------------------------------------------------------------------");
            System.out.println("JSON");
            System.out.println(gson.toJson(request));
            System.out.println("-------------------------------------------------------------------------------------------------------------");

            byte[] base64EncryptedMessage = new RSAEncryption().encrypt(PUBLIC_KEY_BASE64_ENCODED.getBytes(), gson.toJson(request));
            String base64EncryptedMessageString = new String(base64EncryptedMessage);

            System.out.println("ENCRYPTED MESSAGE BASE64");
            System.out.print(base64EncryptedMessageString);
            System.out.println("/END ENCRYPTED MESSAGE BASE64");
        } catch (Exception e) {
            e.printStackTrace();
        }