Modify it to Combobox

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JOptionPane;

import javax.swing.JPanel;

import javax.swing.JTextField;

public class MeterConverter extends JFrame

{

private JPanel panel;

private JLabel Label;

private JTextField TextField;

private JButton feetsButton;

private JButton inchesButton;

private JButton kilometersButton;

private final int WINDOW_WIDTH = 400; private final int WINDOW_HEIGHT = 100;

public MeterConverter()

{

setTitle("Meter Converter");

setSize(WINDOW_WIDTH, WINDOW_HEIGHT);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

buildPanel();

add(panel);

setVisible(true);

}

private void buildPanel()

{

Label = new JLabel("Enter meters");

TextField = new JTextField(10);

feetsButton = new JButton("Convert to feet");

inchesButton = new JButton("Convert to inches");

kilometersButton = new JButton("Convert to kilometers ");

feetsButton.addActionListener(new ButtonListener());

inchesButton.addActionListener(new ButtonListener());

kilometersButton.addActionListener(new ButtonListener());

panel = new JPanel();

panel.add(Label);

panel.add(TextField);

panel.add(feetsButton);

panel.add(inchesButton);

panel.add(kilometersButton);

}

private class ButtonListener implements ActionListener

{

public void actionPerformed(ActionEvent e)

{

String input;

String convertTo = "";

double result = 0.0;

input = TextField.getText();

if (e.getSource() == feetsButton)

{

convertTo = " feets.";

result = Double.parseDouble(input) * 3.28;

}

else if (e.getSource() == inchesButton)

{

convertTo = " inches.";

result = Double.parseDouble(input) * 39.37;

}

else if (e.getSource() == kilometersButton)

{

convertTo = " kilometers.";

result = Double.parseDouble(input) * 0.001;

}

JOptionPane.showMessageDialog(null, input +

" meters is " + result + convertTo);

}

}

}

public class Main {

public static void main(String[] args)

{

new MeterConverter();

}

}