public class AppGUI extends JFrame {

private final List<Player> players;
private JComboBox<Object> cmbPlayers;
private JTextField txtSpin;
private JTextField txtName;
private JTextField txtBalance;
private JTextField txtGuess;
private JTextField txtWager;

private final String fileName;

/**
* Constructor of AppGUI.
* It takes a single parameter string fileName i.e.
* from which player's information is read.
* @param fileName the file containing players
* information.
*/
public AppGUI(String fileName) {

   this.fileName = fileName;

   init();
   players = new ArrayList<>();
   readPlayers();
}

/**
* This method reads players from
* the specified file.
* It assumes the format of player e.g.
*
* name1:balance1
* name2:balance2
* name3:balance3
*/
private void readPlayers() {
   try {
         players.removeAll(players);
         Scanner scanner = new Scanner(new File(fileName));

         while (scanner.hasNextLine()) {
            String s = scanner.nextLine();
            if(s != null) {
               String[] s1 = s.split(":");
               if(s1 != null && s1.length == 2) {
                     Player player = new Player();
                     Float balance = Float.parseFloat(s1[1]);
                     player.setName(s1[0]);
                     player.setBalance(balance);
                     players.add(player);
               }
            }
         }

   } catch (FileNotFoundException e) {
         JOptionPane.showMessageDialog(this,
               fileName + " doesn't exists",
               "File not found",
               JOptionPane.ERROR_MESSAGE);
   }

   cmbPlayers.removeAllItems();
   if(players != null) {
         for (Player player: players) {
            cmbPlayers.addItem(player.getName());
         }
   }
}

/**
* This method is responsible for creating
* user interface.
*/
private void init() {

   setLayout(new GridBagLayout());

   setSize(400, 300);

Building a Rolodex: For this project, we are using JSPs to allow...