Java Swing - distance converter

/*

Create a new Java GUI application to convert miles to kilometers when pressing the "Convert!" button. Note that you need to implement the ActionListener interface and override the actionPerformed() method.  Note that 1 mile is equal to 1.609 kilometers.

*/

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

class Converter implements ActionListener

{

     JFrame jf;

     JLabel L1, L2;

     JTextField tf1, tf2;

     JButton b1;

    

     Converter()

     {

          jf = new JFrame();

         

          jf.setSize(350,200);

          jf.setTitle("Converter");

         

          FlowLayout FL = new FlowLayout(FlowLayout.CENTER,20,20);

          jf.setLayout(FL);

         

          Font f1 = new Font("Freestyle Script", Font.BOLD, 20);

          Font f2 = new Font("Freestyle Script", Font.BOLD, 15);

          Dimension d1 = new Dimension(100,30);

          Dimension d2 = new Dimension(75,30);

          L1 = new JLabel("Miles : ", SwingConstants.RIGHT);

          L2 = new JLabel("Kilometers : ",SwingConstants.RIGHT);

          L1.setFont(f1);

          L1.setPreferredSize(d1);

          L2.setFont(f1);

          L2.setPreferredSize(d1);

         

          tf1=new JTextField("",15);

          tf2=new JTextField("",15);

         

          tf1.setFont(f1);

          tf2.setFont(f1);

         

                  

          b1 = new JButton("Convert!");

          b1.setFont(f2);

          b1.setPreferredSize(d2);

             

          jf.add(L1);

         

          jf.add(tf1);

          jf.add(L2);

          jf.add(tf2);

          jf.add(b1);

         

          b1.addActionListener(this);

                       

          jf.setVisible(true);

          jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

     }

    

    

     public void actionPerformed(ActionEvent ae)

     {

          double m = Double.parseDouble(tf1.getText());

          double km = m*1.609;

         

          tf2.setText(Double.toString(km));

     }

    

     public static void main(String as[])

     {

          new Converter();

     }

}

Output: