public class DatabaseFunctions extends JFrame {


    // This program uses a JTable name jTable to view information from the database

    private DefaultTableModel dataModel;
    private DefaultTableModel checkoutModel;

    private Connection connection;


    public DatabaseFunctions() { // Your constructor

        connect();

        initComponents();

        checkoutModel = (DefaultTableModel) checkoutTable.getModel();
        dataModel = (DefaultTableModel) jTable.getModel();

        populateDataTable("SELECT * FROM TableName");
    }

    private void populateDataTable(String query) {

        // Removes all rows from table
        if (dataModel.getRowCount() > 0) {
            for (int i = dataModel.getRowCount() - 1; i > -1; i--) {
                dataModel.removeRow(i);
            }
        }

        Object rowData[] = new Object[5];
        try {

            connection = ConnectionManager.getInstance().getConnection();

            PreparedStatement preparedStatement
                    = connection.prepareStatement(query);

            ResultSet resultSet = preparedStatement.executeQuery();

            while (resultSet.next()) {

                // These are all names of columns of jTable and the database
                rowData[0] = resultSet.getString("Column1");
                rowData[1] = resultSet.getInt("Column2");
                rowData[2] = resultSet.getString("Column3");
                rowData[3] = resultSet.getInt("Column4");
                rowData[4] = resultSet.getInt("Column5");

                dataModel.addRow(rowData);
            }

        } catch (SQLException sqlExcep) {
            sqlExcep.printStackTrace();
        }

        jTable.repaint();
        jTable.revalidate();

    }

    public void connect(){

      String driver = "org.apache.derby.jdbc.EmbeddedDriver";
      String protocol = "jdbc:derby:";
      String databaseName = "usr/database";
      String url = "jdbc:derby://localhost:1527/database ";

       try {
            Class.forName(driver).newInstance();

            connection = DriverManager.getConnection(url, "brinlee", "brinlee");
            System.out.println("Established connection to database");


        }catch (SQLException sqlExcep){
            sqlExcep.printStackTrace();
            displayErrorMessage("Could not establish connection to database \n" +
                    "SQL Exception");
        }catch (ClassNotFoundException cnfExcep){
            cnfExcep.printStackTrace();
            displayErrorMessage("Could not establish connection to database \n" +
                    "Class Not Found Exception");
        }catch (Exception excep){
            excep.printStackTrace();
            displayErrorMessage("Could not establish connection to database \n" +
                    "Exception");
        }
      }

    }