//v 1.3
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;

public class LoanPayment implements ActionListener {
    JFrame loanPayFrame;
    JPanel loanPayPanel;
    JTextField loan, years, interestRate;
    JLabel loanLabel, yearsLabel, intRateLabel, resultLabel;
    JButton calculate;

    // Constructor
    public LoanPayment() {
	// Create the frame and container.
	loanPayFrame = new JFrame("銀貸清償計算系統  周國華設計");
	loanPayPanel = new JPanel();
	loanPayPanel.setLayout(new GridLayout(4, 2));
	
	// Add the widgets.
	addWidgets();

	// Add the panel to the frame.
	loanPayFrame.getContentPane().add(loanPayPanel, BorderLayout.CENTER);

	// Exit when the window is closed.
        loanPayFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

	// Show the converter.
	loanPayFrame.pack();
	loanPayFrame.setVisible(true);
    }

    // Create and add the widgets for converter.
    private void addWidgets() {
	// Create widgets.
	loan = new JTextField(14);
        years = new JTextField(14);
        interestRate = new JTextField(14);
	loanLabel = new JLabel("貸款總金額 (例：$3,500,000，請填入3500000)", SwingConstants.LEFT);
	yearsLabel = new JLabel("貸款總年數 (例：貸款二十年，請填入20)", SwingConstants.LEFT);
        intRateLabel = new JLabel("貸款年利率 (例：12.5%，請填入12.5)", SwingConstants.LEFT);
        calculate = new JButton("計算>>");
	resultLabel = new JLabel("每月攤還...", SwingConstants.LEFT);

	// Listen to events from Convert button.
	calculate.addActionListener(this);

	// Add widgets to container.
	loanPayPanel.add(loanLabel);
        loanPayPanel.add(loan);
	loanPayPanel.add(yearsLabel);
        loanPayPanel.add(years);
	loanPayPanel.add(intRateLabel);
        loanPayPanel.add(interestRate);
	loanPayPanel.add(calculate);
        loanPayPanel.add(resultLabel);
	
        loanLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
	yearsLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
        intRateLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
        resultLabel.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
	
    }

    // Implementation of ActionListener interface.
    public void actionPerformed(ActionEvent event) {
      	// 計算每月攤還金額
        double monthRate = (Double.parseDouble(interestRate.getText())) / 1200;
        int totalMonth = (Integer.parseInt(years.getText())) * 12;
        double temp1 = Math.pow(1+monthRate , - totalMonth);
        double temp2 = (1 - temp1) / monthRate;
        double result = (Double.parseDouble(loan.getText())) / temp2;
        DecimalFormat myFormatter = new DecimalFormat("$###,###.##");
        String output = myFormatter.format(result);
        resultLabel.setText("每月攤還" + output);
    }

    // main method
    public static void main(String[] args) {
	// Set the look and feel.
	try {
	    UIManager.setLookAndFeel(
		UIManager.getSystemLookAndFeelClassName());
	} catch(Exception e) {}

	LoanPayment pay = new LoanPayment();
    }
}