Как управлять состоянием и сценами#

public class StateStartScene extends Scene {
    @Override
    public State processIncomingMessage(MessageWebhook incomingMessage, State currentState) {
        answerWithText(incomingMessage, "Hello. Tell me your username.");

        return activateNextScene(currentState, new InputUsernameScene());
    }
}

public class InputUsernameScene extends Scene {
    @Override
    public State processIncomingMessage(MessageWebhook incomingMessage, State currentState) {
        var stateData = currentState.getData();

        var username = getText(incomingMessage);
        if (username != null && username.length() <= 20 && username.length() >= 5) {
            stateData.put("username", username);
            currentState.setData(stateData);

            answerWithText(incomingMessage, "Please, send password");

            activateNextScene(currentState, new InputPasswordScene());

        } else {
            answerWithText(incomingMessage, "invalid username");
        }

        return currentState;
    }
}

public class InputPasswordScene extends Scene {
    @Override
    public State processIncomingMessage(MessageWebhook incomingMessage, State currentState) {
        var stateData = currentState.getData();

        var password = getText(incomingMessage);
        if (password != null && password.length() <= 20 && password.length() >= 8) {
            stateData.put("password", password);
            currentState.setData(stateData);

            answerWithText(incomingMessage, String.format("""
                Successful account creation.
                Your username: %s.
                Your password: %s.
                """, stateData.get("username"), password));

            return activateStartScene(currentState);

        } else {
            answerWithText(incomingMessage, "invalid password");
        }

        return currentState;
    }
}