dr_example.java

static class ResultPair {
    String response;
    List<User> altered;
}

public Response subscriptionConfirmed(Message message, int addDays, String messageText, String userFilter) {
    LocalDateTime now = LocalDateTime.now();
    List<User> users = findUsers(message.getFrom(), userFilter);

    ResultPair result = pureLogic(message, addDays, now, users);

    for (User user : result.altered) {
        this.users.saveAndFlush(user);
        this.messageProvider.sendTxt(user.getChatId(), messageText);
    }

    return MainMenu
            .mainMenu(message.getChatId())
            .prepend(new SendMessage(message.getChatId(), result.response));
}

static ResultPair pureLogic(Message message, int addDays, LocalDateTime now, List<User> users) {
    var result = new ResultPair();

    if (message.getText().equals("Да!")) {
        result.altered = users
                .stream()
                .peek(user -> setEndOfSubscription(addDays, now, user))
                .collect(Collectors.toList());
        result.response = alteredUsersReport(
                result.altered,
                "Не нашлось ни одного такого пользователя.",
                "Обновлён пользователь {0}.",
                "Обновлено пользователей: {0} шт."
        );
    } else {
        result.altered = Collections.emptyList();
        result.response = "Охрана, отмена!..";
    }

    return result;
}

static void setEndOfSubscription(int addDays, LocalDateTime now, User user) {
    var sub = user.getSubscription();
    sub.setEndOfSubscription(
            sub.getEndOfSubscription().isBefore(now)
                    ? now.plusDays(addDays)
                    : sub.getEndOfSubscribe().plusDays(addDays)
    );
}