java - テキストフィールド変更時の検証

Question

次のコードを使用して Loan Calculator を作成していますが、ユーザーの入力を検証しようとすると、setText を実行できません。コンパイルエラーは発生しません。動作していません。次のコードがあります。

public class LoanCalculator extends JFrame {
  // Create text fields for interest rate,
// year, loan amount, monthly payment, and total payment
private JTextField jtfAnnualInterestRate = new JTextField("5");
private JTextField jtfNumberOfYears = new JTextField("10");
private JTextField jtfLoanAmount = new JTextField("10000");
private JTextField jtfMonthlyPayment = new JTextField("106.07");
private JTextField jtfTotalPayment = new JTextField("12727.86");

// Create a Compute Payment button
private JButton jbtClear = new JButton("Reset Fields");

public LoanCalculator() {
// Panel p1 to hold labels and text fields
JPanel p1 = new JPanel(new GridLayout(5, 2));
p1.add(new JLabel("Annual Interest Rate"));
p1.add(jtfAnnualInterestRate);
p1.add(new JLabel("Number of Years"));
p1.add(jtfNumberOfYears);
p1.add(new JLabel("Loan Amount"));
p1.add(jtfLoanAmount);
p1.add(new JLabel("Monthly Payment"));
p1.add(jtfMonthlyPayment);
p1.add(new JLabel("Total Payment"));
p1.add(jtfTotalPayment);
p1.setBorder(new
TitledBorder("Enter loan amount, interest rate, and year"));
jtfTotalPayment.setEditable(false);
jtfMonthlyPayment.setEditable(false);

// Panel p2 to hold the button
JPanel p2 = new JPanel(new FlowLayout(FlowLayout.RIGHT));
p2.add(jbtClear);

// Add the panels to the frame
add(p1, BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);

// Register listeners
jbtClear.addActionListener(new ButtonListener());
jtfAnnualInterestRate.getDocument().addDocumentListener(new DocListener());
jtfNumberOfYears.getDocument().addDocumentListener(new DocListener());
jtfLoanAmount.getDocument().addDocumentListener(new DocListener());
}

/** Handle textfield changes */
class DocListener implements DocumentListener {
 public void insertUpdate(DocumentEvent e) { validate(); }
 public void removeUpdate(DocumentEvent e) { }
 public void changedUpdate(DocumentEvent e) { }

 public void validate() {
     //get values from text fields
     double interest = Double.parseDouble(jtfAnnualInterestRate.getText());
 int year = Integer.parseInt(jtfNumberOfYears.getText());
 double loanAmt = Double.parseDouble(jtfLoanAmount.getText());
 Loan loan = new Loan(interest, year, loanAmt);


 //validate field values and shift focus if needed
 if (! (interest >= 1 && interest <= 10)){
     JOptionPane.showMessageDialog(null, 
        "interest must be between 1 and 10 percent");
     jtfAnnualInterestRate.setText("5");                   //THIS DOESN'T RUN
     jtfAnnualInterestRate.requestFocus(true);
 }       
 //display monthly and total payments
 else {
      jtfMonthlyPayment.setText(String.format("%.2f", 
                          loan.getMonthlyPayment()));
      jtfTotalPayment.setText(String.format("%.2f", 
                  loan.getTotalPayment()));
 }
 }
}

/** Handle the Reset button Code not included */
}

public static void main(String[] args) {
 LoanCalculator frame = new LoanCalculator();
 frame.pack();
 frame.setTitle("LoanCalculator");
 Dimension screenSize =
   Toolkit.getDefaultToolkit().getScreenSize();
 int screenWidth = screenSize.width;
int screenHeight = screenSize.height;
// Locate the upper-left corner at (x, y)
int x =  3 * (screenWidth - frame.getWidth()) / 4;
int y = (screenHeight - frame.getHeight()) /2;
frame.setLocation(x, y);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

どこが間違っているのか分かりますか？