Java Programming

import java.awt.BorderLayout.
import java.awt.Color.
import java.awt.Container.
import java.awt.FlowLayout.
import java.awt.Font.
import java.awt.GridLayout.
import java.awt.Window.
import java.awt.event.ActionEvent.
import java.awt.event.ActionListener.
import java.awt.event.WindowAdapter.
import java.awt.event.WindowEvent.

import javax.swing.JButton.
import javax.swing.JDialog.
import javax.swing.JFrame.
import javax.swing.JLabel.
import javax.swing.JMenu.
import javax.swing.JMenuBar.
import javax.swing.JMenuItem.
import javax.swing.JPanel.
import javax.swing.JTextArea.
import javax.swing.JOptionPane.

public class Calculator extends JFrame implements ActionListener
{
// Variables
final int MAX_INPUT_LENGTH = 20.
final int INPUT_MODE = 0.
final int RESULT_MODE = 1.
final int ERROR_MODE = 2.
int displayMode.

boolean clearOnNextDigit, percent.
double lastNumber.
String lastOperator.

private JMenu jmenuFile, jmenuEdit, jmenuView, jmenuHelp.
private JMenuItem jmenuitemExit, jmenuitemCopy, jmenuitemPaste, jmenuitemStd,
jmenuitemSci, jmenuitemDigitGrp, jmenuitemAbout.
private JDialog dialog.

private JLabel display.
private JButton button[].
private JPanel masterPanel.
private JTextArea textarea.

Font f12 = new Font("Times New Roman", 0, 12).
Font f121 = new Font("Times New Roman", 1, 12).


jmenuitemSci = new JMenuItem("Scientific").
jmenuitemSci.setFont(f12).

jmenuitemDigitGrp = new JMenuItem("Digit Grouping").
jmenuitemDigitGrp.setFont(f12).
jmenuView.add(jmenuitemStd).
jmenuView.add(jmenuitemSci).
jmenuView.addSeparator().
jmenuView.add(jmenuitemDigitGrp).

jmenuHelp = new JMenu("Help").
jmenuHelp.setFont(f121).

jmenuitemAbout = new JMenuItem("About Calculator").
jmenuitemAbout.setFont(f12).
jmenuHelp.add(jmenuitemAbout).

JMenuBar mb = new JMenuBar().
// mb.add(jmenuFile).
mb.add(jmenuEdit).
mb.add(jmenuView).
mb.add(jmenuHelp).
setJMenuBar(mb).

//Set frame layout manager

setBackground(Color.gray).

//adds menubar to frame (end)

masterPanel = new JPanel().

display = new JLabel("0").
display.setAlignmentX(JLabel.RIGHT).
display.setBackground(Color.gray).

Container contentPane = getContentPane().

// Add components to frame
contentPane.add(display, BorderLayout.NORTH).

button = new JButton[23].

JPanel backSpace = new JPanel().
backSpace.setLayout(new GridLayout(1, 1, 2, 2)).

button[20] = new JButton("Backspace").
backSpace.add(button[20]).

JPanel control = new JPanel().
control.setLayout(new GridLayout(1, 2, 2 ,2)).

button[21] = new JButton(" CE ").
button[22] = new JButton("C").

control.add(button[21]).
control.add(button[22]).