my{} JAVA skatebord shp gui swing

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package skateshop;

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import javax.swing.BorderFactory;
import javax.swing.ImageIcon;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.ListSelectionModel;
import javax.swing.border.Border;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;

public class SkateShop extends JFrame{

 private JPanel panel1, panel2, panel3, panel4, panel5, panel6;

 private JComboBox decks, trucks, wheels;

 private JScrollPane scroll;
 private JList Misc;

 private ImageIcon skateboard;

 private JLabel picture, subTotalOutput, taxOutput, totalOutput;

 private String[] deck = {"The Master Thrasher $60", "The Dictator $45", "The Street King $50"};
 private String[] truck = {"7.75 inch axle $35", "8 inch axle $40", "8.5 inch axle $45"};
 private String[] wheel = {"51mm $20", "55mm $22", "58mm $24", "61mm $28"};
 private String[] misc = {"Riser pads: $2", "Nuts & bolts kit: $3", "Grip tape: $10", "Bearings: $30"};
 //Use a parallel array to match index from list to match price from this array.
 private double[] prices = {2.0, 3.0, 10.0, 20.0, 22.0, 24.0, 28.0, 30.0, 35.0, 40.0, 45.0, 50.0, 60.0};
  
 private double subtotal, tax, total;

 private DecimalFormat tenths = new DecimalFormat("#0.0#");

 private Border b1 = BorderFactory.createTitledBorder("Choose a Deck");
 private Border b2 = BorderFactory.createTitledBorder("Choose your Trucks");
 private Border b3 = BorderFactory.createTitledBorder("Choose some Wheels");
 private Border b4 = BorderFactory.createTitledBorder("Misc...");
 private Border b6 = BorderFactory.createTitledBorder("Receipt");

 public SkateShop(){
  setLayout(new GridLayout(3, 2));
  panel1 = new JPanel();
  decks = new JComboBox(deck);
  decks.addActionListener(new ComboListener());
  panel1.setBorder(b1);
  panel1.add(decks);
 
  panel2 = new JPanel();
  trucks = new JComboBox(truck);
  trucks.addActionListener(new ComboListener());
  panel2.setBorder(b2);
  panel2.add(trucks);
 
  panel3 = new JPanel();
  wheels = new JComboBox(wheel);
  wheels.addActionListener(new ComboListener());
  panel3.setBorder(b3);
  panel3.add(wheels);
 
  panel4 = new JPanel();
  Misc = new JList(misc);
  Misc.setVisibleRowCount(3);
  Misc.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
  Misc.addListSelectionListener(new ListListener());
  scroll = new JScrollPane(Misc);
  panel4.setBorder(b4);
  panel4.add(scroll);
 
  panel5 = new JPanel();
  skateboard = new ImageIcon("skateboard.png");
  picture = new JLabel();
  picture.setIcon(skateboard);
  panel5.add(picture);
 
  panel6 = new JPanel();
  panel6.setLayout(new GridLayout(3, 0));
  subTotalOutput = new JLabel();
  taxOutput = new JLabel();
  totalOutput = new JLabel();
  panel6.setBorder(b6);
  panel6.add(subTotalOutput);
  panel6.add(taxOutput);
  panel6.add(totalOutput);
 
  add(panel1);
  add(panel2);
  add(panel3);
  add(panel4);
  add(panel5);
  add(panel6);
  setSize(400, 300);
  setTitle("Kevin's Skateshop");
  setVisible(true);
  setDefaultCloseOperation(EXIT_ON_CLOSE);
 }
 public static void main(String[] args) {
  new SkateShop();
 }

 public class ListListener implements ListSelectionListener {

  @Override
  public void valueChanged(ListSelectionEvent e) {
   int[] index = Misc.getSelectedIndices();
   for(int i: index){
    if (i == 0){
     subtotal += prices[0];
    }
    else if (i == 1){
     subtotal += prices[1];
    }
    else if (i == 2){
     subtotal += prices[2];
    }
    else if (i == 3){
     subtotal += prices[7];
    }else{}
   }
  }
 
 }

 public class ComboListener implements ActionListener {
  @Override
  public void actionPerformed(ActionEvent e) {
   if (e.getSource() == decks){
    int index = decks.getSelectedIndex();
    if(index == 0){
     subtotal += prices[12];
    }
    else if(index == 1){
     subtotal += prices[10];
    }
    else if(index == 2){
     subtotal += prices[11];
    }else{}
   }
   else if (e.getSource() == trucks){
    int index = trucks.getSelectedIndex();
    if(index == 0){
     subtotal += prices[8];
    }
    else if(index == 1){
     subtotal += prices[9];
    }
    else if(index == 2){
     subtotal += prices[10];
    }else{}
   }
   else if (e.getSource() == wheels){
    int index = wheels.getSelectedIndex();
    if(index == 0){
     subtotal += prices[3];
    }
    else if(index == 1){
     subtotal += prices[4];
    }
    else if(index == 2){
     subtotal += prices[5];
    }
    else if(index == 3){
     subtotal += prices[6];
    }else{}
   }else{}
   subTotalOutput.setText("Subtotal:  " + "$" + tenths.format(subtotal));
  
   tax = (subtotal * 0.07);
   total = (subtotal + tax);
  
   taxOutput.setText("Tax:  " + "$" + tenths.format(tax));
   totalOutput.setText("Total:  " + "$" + tenths.format(total));
  }
 
 }
}

----

// other code to help fix

class ShopItem {
    public final static DecimalFormat fmt = new DecimalFormat("#0.00");
    private final String name;
    private final double price;
    public ShopItem(String name, double price) {
        this.name = name;
        this.price = price;
    }
    public String toString() { return name + " $" + fmt.format(price); }
    public String getName() { return name; }
    public double getPrice() { return price; }
}

class SkateShop extends JFrame{
    private final int CB_DECK=0, CB_TRUCK=1, CB_WHEELS=2, CB_SIZE=3;
    private final ShopItem[] singles = new ShopItem[CB_SIZE];
    private final java.util.List<ShopItem> misc;
    private final JLabel subTotalOutput, taxOutput, totalOutput;

    public SkateShop(){
        this.subTotalOutput = new JLabel();
        this.taxOutput = new JLabel();
        this.totalOutput = new JLabel();

        setLayout(new GridLayout(3, 2));
        JPanel panel1 = getItemPanel(
            CB_DECK,
            "Choose a Deck",
            new ShopItem [] {
                new ShopItem("The Master Thrasher", 60),
                new ShopItem("The Dictator",  45),
                new ShopItem("The Street King", 50),
            });

        this.misc = new java.util.ArrayList<ShopItem>();
        JPanel panel4 = getListItemPanel(this.misc, "Misc...", 
            new ShopItem [] {
                new ShopItem("Riser pads", 2),
                new ShopItem("Nuts & bolts kit", 3),
                new ShopItem("Grip tape", 10),
                new ShopItem("Bearings", 30),
            });
                
        JPanel panel6 = new JPanel();
        panel6.setLayout(new GridLayout(3, 0));
        panel6.setBorder(BorderFactory.createTitledBorder("Receipt"));
        panel6.add(subTotalOutput);
        panel6.add(taxOutput);
        panel6.add(totalOutput);

        add(panel1);
        add(panel4);
        add(panel6);

        setSize(400, 300);
        setTitle("Kevin's Skateshop");
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        setVisible(true);
    }

    private JPanel getItemPanel(final int index, String name, ShopItem [] items) {
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createTitledBorder(name));
        final JComboBox<ShopItem> cb = new JComboBox<ShopItem>(items);
        cb.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                singles[index] = (ShopItem)cb.getSelectedItem();
                updateTotal();
            }
        });
        panel.add(cb);
        return panel;

    }

    private JPanel getListItemPanel(final java.util.List<ShopItem> chosen, String name, ShopItem [] items) {
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createTitledBorder(name));
        final JList<ShopItem> jlist = new JList<ShopItem>(items);
        jlist.setVisibleRowCount(3);
        jlist.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
  jlist.addListSelectionListener(new ListSelectionListener() {
            public void valueChanged(ListSelectionEvent e) {
                chosen.clear();
                for(ShopItem item : jlist.getSelectedValuesList()) {
                    chosen.add(item);
                }
                updateTotal();
            }
        });
        panel.add(new JScrollPane(jlist));
        return panel;
    }

    private double getSubTotal() {
        double tot = 0;
        for(ShopItem item : singles) { 
            tot += (item==null) ? 0 : item.getPrice();
        }
        for(ShopItem item : misc) { tot += item.getPrice(); }
        return tot;
    }

    private void displayValue(JLabel lab, String name, double value) {
        lab.setText(name + ":  " + "$" + ShopItem.fmt.format(value));
    }

    private void updateTotal() {
        double subtotal = getSubTotal();
        double tax = subtotal * 0.07;
        displayValue(subTotalOutput, "Subtotal", subtotal); 
        displayValue(taxOutput, "Tax", tax);
        displayValue(totalOutput, "Total", subtotal + tax);
    }
}