combo boxes

how do you store numbers in the choices. ex. soda is $.75 and tax is $.07 then it equals a new total. I've been trying to use the Itemlistener but i can't figure out how to store the numbers

import javax.swing.*; import java.awt.*; import java.awt.event.*; import javax.swing.ButtonGroup; import javax.swing.ComboBoxModel; import javax.swing.DefaultComboBoxModel; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JLabel; import javax.swing.JRadioButton; import javax.swing.JTextField;

import javax.swing.WindowConstants; import javax.swing.SwingUtilities;

public class BurgeMenu extends javax.swing.JFrame implements ItemListener
{ private JLabel jLabel1; private JLabel jLabel2; private JLabel jLabel3; private JLabel jLabel4; private JLabel jLabel5; private JRadioButton jRadioButton5; private JRadioButton jRadioButton4; private JRadioButton jRadioButton3; private JRadioButton jRadioButton2; private JRadioButton jRadioButton1; private ButtonGroup buttonGroup1; private JTextField totalbox; private JTextField taxbox; private JTextField subtbox; private JButton jButton1; private JButton jButton2; private JLabel jLabel8; private JLabel jLabel7; private JLabel jLabel6; private JComboBox jComboBox2; private JComboBox jComboBox1; private JTextField sprqst; double Cheeseburger = 2.49; double DoubleCheeseburger = 3.89; double TripleCheeseburger = 4.99; double Medium = .75; double Large = 1.25; double tax = .07; double subtotal; double total;

/**
* Auto-generated main method to display this JFrame
*/
public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            BurgeMenu inst = new BurgeMenu();
            inst.setLocationRelativeTo(null);
            inst.setVisible(true);
        }
    });
}

public BurgeMenu() {
    super();
    initGUI();
}

private void initGUI() {
    try {
        setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
        getContentPane().setLayout(null);
        {
            jLabel1 = new JLabel();
            getContentPane().add(jLabel1);
            jLabel1.setText("McDowell's");
            jLabel1.setBounds(204, 0, 125, 30);
        }
        {
            jLabel2 = new JLabel();
            getContentPane().add(jLabel2);
            jLabel2.setText("ComboMeal");
            jLabel2.setBounds(24, 43, 90, 16);
        }
        {
            jLabel3 = new JLabel();
            getContentPane().add(jLabel3);
            jLabel3.setText("SpecialRequest:");
            jLabel3.setBounds(24, 76, 129, 16);
        }
        {
            jLabel4 = new JLabel();
            getContentPane().add(jLabel4);
            jLabel4.setText("Drinks:");
            jLabel4.setBounds(24, 110, 72, 16);
        }
        {
            sprqst = new JTextField();
            getContentPane().add(sprqst);
            sprqst.setBounds(171, 73, 158, 22);
        }
        {
            ComboBoxModel jComboBox1Model = 
                new DefaultComboBoxModel(
                        new String[] { "1.Cheeseburger", "2.Double Cheeseburger","3.Triple Cheeseburger" });
            jComboBox1 = new JComboBox();
            getContentPane().add(jComboBox1);
            jComboBox1.setModel(jComboBox1Model);
            jComboBox1.setBounds(171, 36, 166, 22);
            jComboBox1.addItemListener(this);
        }
        {
            jLabel5 = new JLabel();
            getContentPane().add(jLabel5);
            jLabel5.setText("Size:");
            jLabel5.setBounds(24, 163, 56, 16);
        }
        {
            ComboBoxModel jComboBox2Model = 
                new DefaultComboBoxModel(
                        new String[] { "Small", "Medium","Large" }); 

            jComboBox2 = new JComboBox();       
            getContentPane().add(jComboBox2);
            jComboBox2.setModel(jComboBox2Model);
            jComboBox2.setBounds(171, 160, 132, 22);
            jComboBox2.addItemListener(this);
        }
        {
            jLabel6 = new JLabel();
            getContentPane().add(jLabel6);
            jLabel6.setText("Subtotal:");
            jLabel6.setBounds(24, 205, 72, 16);
        }
        {
            jLabel7 = new JLabel();
            getContentPane().add(jLabel7);
            jLabel7.setText("Tax:");
            jLabel7.setBounds(24, 245, 56, 16);
        }
        {
            jLabel8 = new JLabel();
            getContentPane().add(jLabel8);
            jLabel8.setText("Total:");
            jLabel8.setBounds(24, 288, 56, 16);
        }
        {
            jButton1 = new JButton();
            getContentPane().add(jButton1);
            jButton1.setText("Submit Order");
            jButton1.setBounds(171, 324, 117, 22);
        }
        {
            jButton2 = new JButton();
            getContentPane().add(jButton2);
            jButton2.setText("Clear");
            jButton2.setBounds(316, 324, 71, 22);
        }
        {
            subtbox = new JTextField();
            getContentPane().add(subtbox);
            subtbox.setBounds(171, 202, 68, 22);
        }
        {
            taxbox = new JTextField();
            getContentPane().add(taxbox);
            taxbox.setBounds(171, 242, 68, 22);
        }
        {
            totalbox = new JTextField();
            getContentPane().add(totalbox);
            totalbox.setBounds(171, 285, 68, 22);
        }
        {
            jRadioButton1 = new JRadioButton();
            getContentPane().add(jRadioButton1);
            jRadioButton1.setText("Coke");
            jRadioButton1.setBounds(171, 108, 60, 20);
            getButtonGroup1().add(jRadioButton1);
        }
        {
            jRadioButton2 = new JRadioButton();
            getContentPane().add(jRadioButton2);
            jRadioButton2.setText("Sprite");
            jRadioButton2.setBounds(171, 131, 64, 20);
            getButtonGroup1().add(jRadioButton2);
        }
        {
            jRadioButton3 = new JRadioButton();
            getContentPane().add(jRadioButton3);
            jRadioButton3.setText("Diet Coke");
            jRadioButton3.setBounds(236, 108, 85, 20);
            getButtonGroup1().add(jRadioButton3);
        }
        {
            jRadioButton4 = new JRadioButton();
            getContentPane().add(jRadioButton4);
            jRadioButton4.setText("Root Beer");
            jRadioButton4.setBounds(235, 131, 82, 20);
            getButtonGroup1().add(jRadioButton4);
        }
        {
            jRadioButton5 = new JRadioButton();
            getContentPane().add(jRadioButton5);
            jRadioButton5.setText("Orange");
            jRadioButton5.setBounds(321, 108, 68, 20);
            getButtonGroup1().add(jRadioButton5);
        }
        pack();
        this.setSize(500, 402);
    } 
    catch (Exception e) 
    {
        //add your error handling code here
        e.printStackTrace();
    }
}

private ButtonGroup getButtonGroup1()
{
    if(buttonGroup1 == null) 
    {
        buttonGroup1 = new ButtonGroup();
    }
    return buttonGroup1;
}

public void itemStateChanged(ItemEvent event) 
{
     if( event.getStateChange( ) == ItemEvent.SELECTED)
            subtbox.setText("");
     else if( event.getStateChange( ) == 1)
            subtbox.setText("Cold");
  }

}