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);
    }

}