public LoyaltySchemeMenu() {

        // Create the CustomerList and add test data.
        customers = new CustomerTestData().createTestData();

        // Create file object with a fixed file name
        filename = new File("d://customerdata.dat");

        // Read the data from the file
        readDataFromFile();

        // Create the ListModel for the JList and add the data to it.
        listCustomers = new DefaultListModel();
        refreshListModel();
        initComponents();


    }

public class CustomerTestData {
    private CustomerList cusList;

    public CustomerList createTestData() {

        cusList = new CustomerList();
        Customer cus;

        cus = new Customer("Daniel", "One", "0001", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Two", "0002", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Three", "0003", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Four", "0004", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Five", "0005", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Six", "0006", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Seven", "0007", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Eight", "0008", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Nine", "0009", "Test1@testmail.com");
        cusList.addCustomer(cus);
        cus = new Customer("Daniel", "Ten", "0010", "Test1@testmail.com");
        cusList.addCustomer(cus);

        return cusList;

    }

    private void refreshListModel() {
        String[] names = customers.getCustomerNames();
        listCustomers.clear();

        for (String c : names) {
            listCustomers.addElement(c);
        }
    }