public class ShopFrame extends JFrame {

    public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                ShopFrame frame = new ShoppingFrame();
                frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

    public ShoppingFrame() {
    setTitle("Shopping Applicationrn");
    // Adaptive window size
    setPreferredSize(new Dimension(this.getWidth(), this.getHeight()));
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 900, 556);
    GridBagLayout gridBagLayout = new GridBagLayout();
    gridBagLayout.columnWidths = new int[]{45, 0, 20, 0, 45, 1, 45, 0, 20, 0, 45, 0};
    gridBagLayout.rowHeights = new int[]{45, 0, 0, 0, 0, 0, 20, 0, 0, 20, 0, 0, 20, 0, 30, 0, 45, 0};
    gridBagLayout.columnWeights = new double[]{0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 0.0, Double.MIN_VALUE};
    gridBagLayout.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE};
    getContentPane().setLayout(gridBagLayout);

    JPanel panel = new JPanel();
    panel.setMinimumSize(new Dimension(5, 20));
    panel.setBackground(SystemColor.scrollbar);
    GridBagConstraints gbc_panel = new GridBagConstraints();
    gbc_panel.gridheight = 17;
    gbc_panel.insets = new Insets(0, 0, 0, 5);
    gbc_panel.fill = GridBagConstraints.BOTH;
    gbc_panel.gridx = 5;
    gbc_panel.gridy = 0;
    getContentPane().add(panel, gbc_panel);

    //Importer.productsModel.addElement("This gets added to the empty DefaultListModel, but not the Importer Class's info.");
    JList<String> productBox = new JList<String>(Importer.productsModel);
    GridBagConstraints gbc_list = new GridBagConstraints();
    gbc_list.gridheight = 4;
    gbc_list.gridwidth = 3;
    gbc_list.insets = new Insets(0, 0, 5, 5);
    gbc_list.fill = GridBagConstraints.BOTH;
    gbc_list.gridx = 1;
    gbc_list.gridy = 2;
    getContentPane().add(productBox, gbc_list);

class Importer {

// Declarations
public static ArrayList<Product> productList = new ArrayList<Product>();
public static DefaultListModel<String> productsModel = new DefaultListModel<String>();

// Connect to database
private static Connection connect = null;

// Running parts of SQL
private static Statement statement = null;

// Running parts of SQL that take parameters
private static PreparedStatement preparedStatement = null;

// Result from a SELECT CELL statement
private static ResultSet resultSetProducts = null;
}

public static void main(String[] args) {
    try {
        connect = DriverManager.getConnection(
                "jdbc:mysql://localhost/shop?useSSL=true"
                + "&user=root&password=Pa$$");

        statement = connect.createStatement();

        // This imports products into a collection
        resultSetProducts = statement.executeQuery(
                "select * from supermarketx.products");
        exportProductsAsCollection(resultSetProducts, productList, productsModel);

        connect.close();

    } catch (Exception e) {
        System.out.println(e);
    }
}

public static void exportProductsAsCollection(ResultSet resultSetProducts, ArrayList<Product> productList, DefaultListModel<String> productModel) throws SQLException {

    while (resultSetProducts.next()) {
        // Adds each product object (Product) into ArrayList
        productList.add(new Product(resultSetProducts.getString("ProductName"), resultSetProducts.getDouble("Price")));
    }
      // Exports names of products for use in JList
      String[] arr = new String[productList.size()];
      for (int i = 0; i < arr.length; i++)
      {
         arr[i] = productList.get(i).getProductName();
         productModel.addElement(arr[i]);
         // To test
     System.out.println(arr[i]);
      }
    }