从 Array[] 填充 JList

Question

好吧，伙计们，对即将发生的文字墙感到抱歉，但我有一个非常烦人的问题，我似乎无法解决。我目前正在尝试从 String[] 填充 JList，但流血的东西拒绝填充。我的程序愉快地写入我的源文件，并愉快地从中读取（它向我抛出 0 个错误），但是当我实际尝试用包含的数据填充我的 JList 时......好吧，什么也没有发生，它只是拒绝做任何事。您能看一下代码，并尝试帮我找出问题吗？我真的不知道为什么这个极其简单的任务给我带来了这么多问题。

package loyaltyguis;

import javax.swing.DefaultListModel;
import loyaltyscheme.CustomerList;
import loyaltyscheme.Customer;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import javax.swing.JOptionPane;
import loyaltyguis.MainForm;

/**
 *
 * @author Liam
 */
public class MainForm extends javax.swing.JFrame {

    public static CustomerList cust;
    private DefaultListModel lModel;

    private File filename;
    private FileInputStream inputFile;
    private ObjectInputStream objectInput;


    /** Creates new form MainForm */
    public MainForm() {
        filename = new File("\\customer_list.dat");
        readDataFromFile();

        lModel = new DefaultListModel();
        cust = new CustomerList();       

        refreshList();
        initComponents();


    }   

    private void readDataFromFile() {
        try {
            inputFile = new FileInputStream(filename);
            objectInput = new ObjectInputStream(inputFile);
            cust = (CustomerList)objectInput.readObject();
            objectInput.close();
        }
        catch (IOException e) {
            JOptionPane.showMessageDialog(this, e.getMessage(),
                    "I/O Error", JOptionPane.ERROR_MESSAGE);
        }
        catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public void refreshList()
    {
        String [] customers = cust.getCustomerNames();
        lModel.clear();   

        for(String m: customers)
        {
            lModel.addElement(m);
        }        
    }


    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        buttonGroup1 = new javax.swing.ButtonGroup();
        jLabel1 = new javax.swing.JLabel();
        jPanel1 = new javax.swing.JPanel();
        tbFirstName = new javax.swing.JTextField();
        tbLastName = new javax.swing.JTextField();
        tbEmail = new javax.swing.JTextField();
        tbNumber = new javax.swing.JTextField();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        btnEdit = new javax.swing.JButton();
        btnSave = new javax.swing.JButton();
        btnDelete = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        lstDisplay = new javax.swing.JList();
        jPanel2 = new javax.swing.JPanel();
        tbCurrPoints = new javax.swing.JTextField();
        jLabel6 = new javax.swing.JLabel();
        jLabel7 = new javax.swing.JLabel();
        jTextField1 = new javax.swing.JTextField();
        btnAddPoints = new javax.swing.JButton();
        btnRedeemPoints = new javax.swing.JButton();
        rdSales1 = new javax.swing.JRadioButton();
        rdSales2 = new javax.swing.JRadioButton();
        jPanel3 = new javax.swing.JPanel();
        btnAddNewCus = new javax.swing.JButton();
        btnExit = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setFont(new java.awt.Font("Tahoma", 1, 18)); // NOI18N
        jLabel1.setText("Customer Loyalty Points");

        jPanel1.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));

        tbFirstName.setText(" ");
        tbFirstName.setEnabled(false);

        tbLastName.setText(" ");
        tbLastName.setEnabled(false);

        tbEmail.setText(" ");
        tbEmail.setEnabled(false);

        tbNumber.setText(" ");
        tbNumber.setEnabled(false);

        jLabel2.setText("First Name(s)");

        jLabel3.setText("Last Name");

        jLabel4.setText("Email");

        jLabel5.setText("Telephobe Number");

        btnEdit.setText("Edit");
        btnEdit.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnEditActionPerformed(evt);
            }
        });

        btnSave.setText("Save");
        btnSave.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnSaveActionPerformed(evt);
            }
        });

        btnDelete.setText("Delete");

        lstDisplay.setModel(lModel);
        jScrollPane1.setViewportView(lstDisplay);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 221, Short.MAX_VALUE)
                    .addComponent(btnDelete, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 221, Short.MAX_VALUE)
                    .addGroup(javax.swing.GroupLayout.Alignment.LEADING, jPanel1Layout.createSequentialGroup()
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                            .addComponent(btnEdit, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(tbNumber, javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(tbEmail, javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(tbLastName, javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(tbFirstName, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 105, Short.MAX_VALUE))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addComponent(jLabel4)
                            .addComponent(jLabel3)
                            .addComponent(jLabel2)
                            .addComponent(jLabel5, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(btnSave, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))))
                .addContainerGap())
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 224, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(tbFirstName, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel2))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(tbLastName, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel3))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(tbEmail, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(tbNumber, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel5))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btnEdit)
                    .addComponent(btnSave))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(btnDelete)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        jPanel2.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));

        tbCurrPoints.setText(" ");

        jLabel6.setText("Current Points");

        jLabel7.setText("Points to Add / Redeem");

        jTextField1.setText(" ");

        btnAddPoints.setText("Add Points");

        btnRedeemPoints.setText("Redeem Points");

        buttonGroup1.add(rdSales1);
        rdSales1.setText("Sales Cat 1");

        buttonGroup1.add(rdSales2);
        rdSales2.setText("Sales Cat 2");

        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(btnAddPoints, javax.swing.GroupLayout.DEFAULT_SIZE, 216, Short.MAX_VALUE)
                    .addComponent(jLabel6)
                    .addComponent(tbCurrPoints, javax.swing.GroupLayout.DEFAULT_SIZE, 216, Short.MAX_VALUE)
                    .addComponent(jLabel7)
                    .addComponent(jTextField1, javax.swing.GroupLayout.DEFAULT_SIZE, 216, Short.MAX_VALUE)
                    .addComponent(btnRedeemPoints, javax.swing.GroupLayout.DEFAULT_SIZE, 216, Short.MAX_VALUE)
                    .addGroup(jPanel2Layout.createSequentialGroup()
                        .addComponent(rdSales1)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 30, Short.MAX_VALUE)
                        .addComponent(rdSales2)))
                .addContainerGap())
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addGap(12, 12, 12)
                .addComponent(jLabel6)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(tbCurrPoints, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jLabel7)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(3, 3, 3)
                .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(rdSales1)
                    .addComponent(rdSales2))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(btnAddPoints)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(btnRedeemPoints)
                .addContainerGap(18, Short.MAX_VALUE))
        );

        jPanel3.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));

        btnAddNewCus.setText("Add New Customer");
        btnAddNewCus.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnAddNewCusActionPerformed(evt);
            }
        });

        btnExit.setText("Exit Program");
        btnExit.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnExitActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
        jPanel3.setLayout(jPanel3Layout);
        jPanel3Layout.setHorizontalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel3Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(btnExit, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 216, Short.MAX_VALUE)
                    .addComponent(btnAddNewCus, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 216, Short.MAX_VALUE))
                .addContainerGap())
        );
        jPanel3Layout.setVerticalGroup(
            jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel3Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(btnAddNewCus, javax.swing.GroupLayout.PREFERRED_SIZE, 36, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(btnExit, javax.swing.GroupLayout.PREFERRED_SIZE, 39, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
                    .addComponent(jLabel1))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel1)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(98, 98, 98))
                    .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

private void btnExitActionPerformed(java.awt.event.ActionEvent evt) {                                        
// TODO add your handling code here:
    System.exit(0);
}                                       


private void btnEditActionPerformed(java.awt.event.ActionEvent evt) {                                        
// TODO add your handling code here:
    tbFirstName.enable(true);
    tbLastName.enable(true);
    tbEmail.enable(true);
    tbNumber.enable(true);
}                                       

private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {                                        
// TODO add your handling code here:
    tbFirstName.enable(false);
    tbLastName.enable(false);
    tbEmail.enable(false);
    tbNumber.enable(false);
}                                       

private void btnAddNewCusActionPerformed(java.awt.event.ActionEvent evt) {                                             
// TODO add your handling code here:

}                                            

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new MainForm().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify                     
    private javax.swing.JButton btnAddNewCus;
    private javax.swing.JButton btnAddPoints;
    private javax.swing.JButton btnDelete;
    private javax.swing.JButton btnEdit;
    private javax.swing.JButton btnExit;
    private javax.swing.JButton btnRedeemPoints;
    private javax.swing.JButton btnSave;
    private javax.swing.ButtonGroup buttonGroup1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JLabel jLabel7;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JList lstDisplay;
    private javax.swing.JRadioButton rdSales1;
    private javax.swing.JRadioButton rdSales2;
    private javax.swing.JTextField tbCurrPoints;
    private javax.swing.JTextField tbEmail;
    private javax.swing.JTextField tbFirstName;
    private javax.swing.JTextField tbLastName;
    private javax.swing.JTextField tbNumber;
    // End of variables declaration                   
}

这也是我用于填充数组的类（ CustomerList ）：

package loyaltyscheme;

import java.util.ArrayList;

/**
 * CustomerList - holds details of all the customers enrolled in the loyalty
 * scheme. The current implementation is based on a simple ArrayList.
 * @author Liam
 */
public class CustomerList {
    private ArrayList<Customer> list;
    /**
     * An integer indicating that a deletion was successful.
     */
    public static final int CUSTOMERDELETED = 0;
    /**
     * An integer indicating that an attempt to delete a customer was
     * unsuccessful because the index was out of range of the collection.
     */
    public static final int INVALIDINDEX = 1;
    /**
     * An integer indicating that a customer could not be deleted because
     * the customer still has unused points.
     */
    public static final int POINTSNOTZERO = 2;

    /**
     * Constructor - creates a new empty collection of customers,
     * currently uses an ArrayList.
     */
    public CustomerList() {
        list = new ArrayList<Customer>();
    }

    /**
     * Retrieves the full name of each customer.
     * @return - a String array containing the full name of each customer,
     * in the order in which they are stored in the collection.
     */
    public String[] getCustomerNames() {
        String names[] = new String[list.size()];
        int pos = 0;
        for (Customer customer : list) {
            names[pos] = customer.getFullName();
            pos ++;
        }
        return names;
    }

    /**
     * Retrieves a customer from a particular location in the list.  The index
     * gives the location required (numbered starting from zero).
     * @param index - the location of the customer required, in the range
     * 0 to (list size - 1).
     * @return - the Customer object at the given position in the collection.
     * If the index passed in by the parameter is outside the range of the
     * collection, the value 'null' will be returned.
     */
    public Customer getCustomerAt(int index) {
        if (index < 0 || index >= list.size())
            return null;
        else
            return list.get(index);                    
    }

    /**
     * Adds a customer to the end of the collection.
     * @param customer - the new Customer object to be added.
     */
    public void addCustomer(Customer customer) {
        list.add(customer);
    }

    /**
     * Removes the customer at the location indicated by the parameter.
     * @param index - the location of the customer to be removed.
     * @return - an integer indicating
     */
    public int removeCustomerAt(int index) {
        if (index < 0 || index >= list.size())
            return INVALIDINDEX;
        else if (list.get(index).getCurrentPoints() != 0)
            return POINTSNOTZERO;
        else {
            list.remove(index);
            return CUSTOMERDELETED;
        }
    }

    /**
     * Retrieves the grand total of unredeemed points held by all customers
     * in the scheme.
     * @return - the total number of points.
     */
    public int getTotalPoints() {
        int points = 0;
        for (Customer customer : list)
            points += customer.getCurrentPoints();
        return points;
    }

    /**
     * Finds out the size of the collection.
     * @return - the number of customers in the list.
     */
    public int size() {
        return list.size();
    }

    /**
     * Returns details of the current state of the collection.
     * @return - a string containing the total size of the list and the
     * total number of points held by all the customers.
     */
    @Override
    public String toString() {
        return "CustomerList{has " + size() + " customers and "
                + getTotalPoints() + " points"
                + '}';
    }
}

抱歉，如果我错过了如此简单的可笑的东西，但这让我发疯，我只是无法发现问题，因为它不是'根本不会抛出任何错误，它只是根本没有这样做。

Answer 1

我在您的代码中没有看到任何告诉图形更新的地方。您只需将其添加到 refreshList 方法中：

public void refreshList() {
  ...
  repaint(g);
}

g 是一个 Graphics 对象，我认为您也没有。阅读 文档如果这不起作用。