Hi Hina,

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.Component;

public class Calc {
public static void main(String[] args) {
System.out.println("This is simple calculator program.");
class CalcGUI extends JFrame {
private final Font BIGGER_FONT = new Font("monspaced", Font.PLAIN, 20);
private JTextField textfield;
private boolean m_startNumber = true;
private String str = "=";
private CalcLogic m_logic = new CalcLogic();
public CalcGUI() {
//--- Display field
textfield = new JTextField("0", 12);
textfield.setHorizontalAlignment(JTextField.RIGHT);
textfield.setFont(BIGGER_FONT);
//--- Clear button
JButton clearButton = new JButton("Clear");
clearButton.setFont(BIGGER_FONT);
clearButton.addActionListener(new ClearListener());
//--- One listener for all numeric keys.
ActionListener numListener = new NumListener();
String buttonOrder = "7894561230.";
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(5, 3, 5, 5));
for (int i = 0; i < buttonOrder.length(); i++) {
String keyTop = buttonOrder.substring(i, i+1);
if(keyTop.equals(" ")){
buttonPanel.add(new JLabel(""));
}else{
JButton b = new JButton(keyTop);
b.addActionListener(numListener);
b.setFont(BIGGER_FONT);
buttonPanel.add(b);
}
}
ActionListener opListener = new OpListener();
JPanel opPanel = new JPanel();
opPanel.setLayout(new GridLayout(5, 1, 5, 5));
String[] opOrder = {"+", "-", "*", "/", "="};
for (int i = 0; i < opOrder.length; i++) {
JButton b = new JButton(opOrder[i]);
b.addActionListener(opListener);
b.setFont(BIGGER_FONT);
opPanel.add(b);
}
//--- Layout the top-level panel.
JPanel con = new JPanel();
con.setLayout(new BorderLayout(5, 5));
con.add(textfield, BorderLayout.NORTH );
con.add(buttonPanel, BorderLayout.CENTER);
con.add(opPanel, BorderLayout.EAST );
con.add(clearButton, BorderLayout.SOUTH );
//--- Finish building the window (JFrame)
this.setContentPane(con);
this.setTitle("Simple Calculator example");
this.setResizable(false);
}//end constructor
private void actionMethod() {
m_startNumber = true;
textfield.setText("0");
str = "=";
m_logic.setTotal("0");
}

class OpListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (m_startNumber) {
actionMethod();
textfield.setText("ERROR - No operator");
} else {
m_startNumber = true;
try {
String displayText = textfield.getText();
if(str.equals("=")) {
m_logic.setTotal(displayText);
} else if(str.equals("+")) {
m_logic.add(displayText);
} else if(str.equals("-")) {
m_logic.subtract(displayText);
} else if(str.equals("*")) {
m_logic.multiply(displayText);
} else if(str.equals("/")) {
m_logic.divide(displayText);
}
textfield.setText("" + m_logic.getTotalString());

} catch (NumberFormatException ex) {
actionMethod();
textfield.setText("Error");
}
str = e.getActionCommand();
}//endif m_startNumber
}//endmethod
}//end class
class NumListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
String digit = e.getActionCommand();
if (m_startNumber) {
textfield.setText(digit);
m_startNumber = false;
} else {
textfield.setText(textfield.getText() + digit);
}
}
}
class ClearListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
actionMethod();
}
}
}
JFrame window = new CalcGUI();
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
window.setSize(300,300);
window.setMinimumSize(true);
window.setMaximumSize(true);

}
}

CalcLogic.java

public class CalcLogic {
//-- Instance variables.
private int total;
public CalcLogic() {
total = 0;
}
public String getTotalString() {
return ""+total;
}
public void setTotal(String n) {
total = convertToNumber(n);
}
public void add(String n) {
total += convertToNumber(n);
}
public void subtract(String n) {
total -= convertToNumber(n);
}
public void multiply(String n) {
total *= convertToNumber(n);
}
public void divide(String n) {
total /= convertToNumber(n);
}
private int convertToNumber(String n) {
return Integer.parseInt(n);
}
}

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Read for more information.

http://www.roseindia.net/java/

Thanks.