Java 设计一个贷款计算器 简易

 import javax.swing.*;
 import java.awt.*;
 import java.awt.event.*;
 import javax.swing.border.*;

 public class LoanCalculator extends JFrame {
     private class ButtonListener implements ActionListener {
         @Override
         public void actionPerformed(ActionEvent e) {
             // TODO Auto-generated method stub
             double interest=
                     Double.parseDouble(jtfAnnualInterestRate.getText());
             int year=
                     Integer.parseInt(jtfNumberOfYears.getText());
             double loanAmount=
                     Double.parseDouble(jtfLoanAmount.getText());

             double monthlyInterest=interest/1200;
             double monthlyPayment= loanAmount*monthlyInterest/(1-1/Math.pow(1+monthlyInterest,
                     year*12));
             double totalPayment=monthlyPayment*year*12;

             jtfMonthlyPayment.setText(String.format("%.2f", monthlyPayment));
             jtfTotalPayment.setText(String.format("%.2f", totalPayment));
         }
     }

     private JTextField jtfAnnualInterestRate=new JTextField();
     private JTextField jtfNumberOfYears=new JTextField();
     private JTextField jtfLoanAmount=new JTextField();
     private JTextField jtfMonthlyPayment=new JTextField();
     private JTextField jtfTotalPayment=new JTextField();

     private JButton jbtComputeLoan=new JButton("Compute Payment");

     public LoanCalculator(){
         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"));

         JPanel p2=new JPanel(new FlowLayout(FlowLayout.RIGHT));
         p2.add(jbtComputeLoan);
         add(p1,BorderLayout.CENTER);
         add(p2,BorderLayout.SOUTH);
         jbtComputeLoan.addActionListener(new ButtonListener());

     }

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         LoanCalculator frame=new LoanCalculator();
         frame.setTitle("LoanCalculator");
         frame.pack();
         frame.setLocationRelativeTo(null);
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);
     }

 }