Передача значения переменной из метода

Есть 3 класса: ApiConfig, ApiData и ApiSteps.

В ApiConfig инициализирована переменная appId.

В ApiData он используется в конструкторе для отправки json.

В ApiSteps в методе получается ее значение из ответа json.

Затем в другом методе отправляется json из ApiData уже с новым значением. Проблема в том, что отправляется id: 0. Хотя если присвоить ей вручную значение в ApiConfig, то все ок. Как сделать так, чтобы значение, полученное в методе, сохранялось и передавалось в теле json?

class ApiConfig
{
  int appId;
  String getProd = url + path + "/loans/orders";
  String sendApp = url + path + "/loans/orders/" + appId + "/send";
}

class ApiData
{
  class Items
  {
    String name;
    String quantity;
    String price;
    Items (String name, String quantity, String price)
    {
      this.name = name;
      this.quantity = quantity;
      this.price = price;
    }
  }
  class Cart
  {
    List <Items> items;
    String shop_order_id;
    int total_price;
    Cart (List <Items> items, String shop_order_id, int total_price)
    {
      this.items = items;
      this.shop_order_id = shop_order_id;
      this.total_price = total_price;
      items.add (new Items ("Смартфон Apple iPhone", "1", "70000"));
    }
  }
  List <Items> items = new ArrayList <> ();
  Cart cart = new Cart (items, "demoPage_338191", 70000);
  String cartObj = apiConfig.gson.toJson (cart);
  class Application_express
  {
    String name;
    String surname;
    String patronymic;
    String sex;
    String birthday;
    String cell_phone;
    String email;
    int employment_income;
    String document_series;
    String document_number;
    String document_date;
    int loan_period;
    boolean sms_notification;
    boolean life_insurance;
    boolean work_insurance;
    boolean deferred_payment;
    int initial_payment;
    Application_express (String name, String surname, String patronymic, String
      sex, String birthday, String cell_phone, String email, int
                           employment_income, String document_series,
                         String document_number, String document_date, int loan_period, boolean
                           sms_notification, boolean life_insurance, boolean work_insurance, boolean
                           deferred_payment, int initial_payment)
    {
      this.name = name;
      this.surname  = surname;
      this.patronymic = patronymic;
      this.sex = sex;
      this.birthday = birthday;
      this.cell_phone = cell_phone;
      this.email = email;
      this.employment_income = employment_income;
      this.document_series = document_series;
      this.document_number = document_number;
      this.document_date = document_date;
      this.loan_period = loan_period;
      this.sms_notification = sms_notification;
      this.life_insurance = life_insurance;
      this.work_insurance = work_insurance;
      this.deferred_payment = deferred_payment;
      this.initial_payment = initial_payment;
    }
  }
  Application_express application_express = new Application_express ("Иван",
    "Иванов", "Иванович", "1", "1990-01-01", "9031111112", "ivan@mail.ru",
    100000, "4528", "123456", "2019-01-01", 12, false,
    false, false, true, 0);
  String appExpObj = apiConfig.gson.toJson (application_express);
  class Orders
  {
    Cart cart;
    Application_express application_express;
    Orders (Cart cart, Application_express application_express)
    {
      this.cart = cart;
      this.application_express = application_express;
    }
  }
  Orders orders = new Orders (cart, application_express);
  String orderObj = apiConfig.gson.toJson (orders);
  class Product
  {
    int product_id;
    Product (int product_id)
    {
      this.product_id = product_id;
    }
  }
  class Application
  {
    int id;
    List <Product> products;
    Cart cart;
    Application_express application_express;
    Application (int id, List <Product> products, Cart cart,
                 Application_express application_express)
    {
      this.id = id;
      this.products = products;
      this.cart = cart;
      this.application_express = application_express;
      products.add (new Product (163));
      products.add (new Product (145));
      products.add (new Product (146));
      products.add (new Product (151));
      products.add (new Product (161));
      products.add (new Product (165));
    }
  }
  List <Product> products = new ArrayList <> ();
  Application Application = new Application (apiConfig.appId, products,
    cart, application_express);
  String appObj = apiConfig.gson.toJson (Application);
}

class ApiSteps
{
  void getProd ()
  {
    apiConfig.request.body (apiData.orderObj);
    apiConfig.request.header ("Content-Type", contType);
    apiConfig.response = apiConfig.request.post (apiConfig.getProd);
    statCode = apiConfig.response.getStatusCode ();
    Assert.assertEquals (statCode, apiData.statCode);
    statLine = apiConfig.response.getStatusLine ();
    Assert.assertEquals (statLine, apiData.statLine);
    contType = apiConfig.response.getContentType ();
    Assert.assertEquals (contType, apiData.contType);
    apiConfig.responseBody = apiConfig.response.getBody ();
    responseBodyAsString = apiConfig.responseBody.asString ();
    Assert.assertEquals (true, responseBodyAsString.contains ("id"));
    Assert.assertEquals (true, responseBodyAsString.contains ("credit_period"));
    Assert.assertEquals (true, responseBodyAsString.contains ("credit_size"));
    Assert.assertEquals (true, responseBodyAsString.contains ("initial_payment"));
    Assert.assertEquals (true, responseBodyAsString.contains ("payment"));
    apiConfig.jsonPath = apiConfig.response.jsonPath ();
    apiConfig.setAppId (apiConfig.jsonPath.get ("id"));
    apiData.Application.id = apiConfig.jsonPath.get ("id");
    apiData.appObj = apiConfig.gson.toJson (apiData.Application);
    apiData.products = apiConfig.jsonPath.get ("products.product.id");
  }
  void sendApp ()
  {
    apiConfig.request.body (apiData.appObj);
    System.out.println (apiData.appObj);
    apiConfig.request.header ("Content-Type", contType);
    apiConfig.response = apiConfig.request.post (apiConfig.sendApp);
    statCode = apiConfig.response.getStatusCode ();
    Assert.assertEquals (statCode, apiData.statCode);
    statLine = apiConfig.response.getStatusLine ();
    Assert.assertEquals (statLine, apiData.statLine);
    contType = apiConfig.response.getContentType ();
    Assert.assertEquals (contType, apiData.contType);
    apiConfig.responseBody = apiConfig.response.getBody ();
    responseBodyAsString = apiConfig.responseBody.asString ();
  }
}