17.6

import java.awt.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.io.FileNotFoundException;

import javax.swing.*;

public class Test_17_6 extends JFrame{
    private JPanel JP1 = new JPanel();
    private JPanel JP2 = new JPanel();
    private JLabel jl1 = new JLabel("Mile");
    private JLabel jl2 = new JLabel("KiloMeter");
    private JTextField jtf1 = new JTextField(10);
    private JTextField jtf2 = new JTextField(10);
    private Double distance;

    public Test_17_6(){
        JP1.setLayout(new GridLayout(2,1));
        jtf1.setHorizontalAlignment(JTextField.RIGHT);
        jtf2.setHorizontalAlignment(JTextField.RIGHT);
        JP1.add(jl1);
        JP1.add(jl2);
        JP2.setLayout(new GridLayout(2,1));
        JP2.add(jtf1);
        JP2.add(jtf2);

        add(JP1,BorderLayout.CENTER);
        add(JP2,BorderLayout.EAST);

        //add listener
        jtf1.addKeyListener(new KeyAdapter(){

            @Override
            public void keyPressed(KeyEvent e) {
                // TODO Auto-generated method stub
                if(e.getKeyCode() == KeyEvent.VK_ENTER)
                {
                    distance = 1.609344 * Double.parseDouble(jtf1.getText());
                    jtf2.setText(String.valueOf(distance));
                }
            }
        });
        jtf2.addKeyListener(new KeyAdapter(){

            @Override
            public void keyPressed(KeyEvent e) {
                // TODO Auto-generated method stub
                if(e.getKeyCode() == KeyEvent.VK_ENTER)
                {
                    distance =  Double.parseDouble(jtf2.getText()) / 1.609344;
                    jtf1.setText(String.valueOf(distance));
                }
            }
        });
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Test_17_6 frame = new Test_17_6();
        frame.setTitle("Test_17_6");
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

}