Perimeter and Area of a Rectangle - Java Sample Program

//Given the length and width of a rectangle, this Java program determines its area and perimeter.
//Filename: RectangleProgram.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class RectangleProgram extends JFrame
{
private JLabel lengthL, widthL, areaL, perimeterL;
private JTextField lengthTF, widthTF, areaTF, perimeterTF;
private JButton calculateB, exitB;
private CalculateButtonHandler cbHandler;
private ExitButtonHandler ebHandler;

private static final int WIDTH = 400;
private static final int HEIGHT = 300;

public RectangleProgram()
{
//Create the four labels
lengthL = new JLabel("Enter the length: ", SwingConstants.RIGHT);
widthL = new JLabel("Enter the width: ",SwingConstants.RIGHT);
areaL = new JLabel("Area: ", SwingConstants.RIGHT);
perimeterL = new JLabel("Perimeter: ", SwingConstants.RIGHT);

//Create the four text fields
lengthTF = new JTextField(10);
widthTF = new JTextField(10);
areaTF = new JTextField(10);
perimeterTF = new JTextField(10);

//Create Calculate Button
calculateB = new JButton("Calculate");
cbHandler = new CalculateButtonHandler();
calculateB.addActionListener(cbHandler);

//Create Exit Button
exitB = new JButton("Exit");
ebHandler = new ExitButtonHandler();
exitB.addActionListener(ebHandler);

//Set the title of the window
setTitle("Area and Perimeter of a Rectangle");

//Get the container
Container pane = getContentPane();

//Set the layout
pane.setLayout(new GridLayout(5, 2));

//Place the components in the pane
pane.add(lengthL);
pane.add(lengthTF);
pane.add(widthL);
pane.add(widthTF);
pane.add(areaL);
pane.add(areaTF);
pane.add(perimeterL);
pane.add(perimeterTF);
pane.add(calculateB);
pane.add(exitB);

//Set the size of the window and display it
setSize(WIDTH, HEIGHT);
setVisible(true);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}

private class CalculateButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
double width, length, area, perimeter;
length = Double.parseDouble(lengthTF.getText());
width = Double.parseDouble(widthTF.getText());
area = length * width;
perimeter = 2 * (length + width);
areaTF.setText("" + area);
perimeterTF.setText("" + perimeter);
}
}

private class ExitButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
System.exit(0);
}
}

public static void main(String[] args)
{
RectangleProgram rectObject = new RectangleProgram();
}
}


***************Sample Output***************