Hi friend,

import javax.swing.*;

public class Calc {
public static void main(String[] args) {
JFrame window = new CalcGUI();
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
}//end main
}
-------------------

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

class CalcGUI extends JFrame {
private final Font BIGGER_FONT = new Font("monspaced", Font.PLAIN, 20);

private JTextField m_displayField;

private boolean m_startNumber = true;
private String m_previousOp = "=";
private CalcLogic m_logic = new CalcLogic();

public CalcGUI() {
//--- Display field
m_displayField = new JTextField("0", 12);
m_displayField.setHorizontalAlignment(JTextField.RIGHT);
m_displayField.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 = "789456123 0 ";
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 content = new JPanel();
content.setLayout(new BorderLayout(5, 5));
content.add(m_displayField, BorderLayout.NORTH );
content.add(buttonPanel , BorderLayout.CENTER);
content.add(opPanel , BorderLayout.EAST );
content.add(clearButton , BorderLayout.SOUTH );
//--- Finish building the window (JFrame)
this.setContentPane(content);
this.pack();
this.setTitle("Simple Calculator");
this.setResizable(false);
}//end constructor
private void action_clear() {
m_startNumber = true;
m_displayField.setText("0");
m_previousOp = "=";
m_logic.setTotal("0");
}
class OpListener implements ActionListener {
public void actionPerformed(ActionEvent e) {

if (m_startNumber) {
action_clear();
m_displayField.setText("ERROR - No operator");
} else {
m_startNumber = true;
try {
String displayText = m_displayField.getText();

if (m_previousOp.equals("=")) {
m_logic.setTotal(displayText);
} else if (m_previousOp.equals("+")) {
m_logic.add(displayText);
} else if (m_previousOp.equals("-")) {
m_logic.subtract(displayText);
} else if (m_previousOp.equals("*")) {
m_logic.multiply(displayText);
} else if (m_previousOp.equals("/")) {
m_logic.divide(displayText);
}

m_displayField.setText("" + m_logic.getTotalString());

} catch (NumberFormatException ex) {
action_clear();
m_displayField.setText("Error");
}
m_previousOp = e.getActionCommand();
}//endif m_startNumber
}//endmethod
}//end class

class NumListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
String digit = e.getActionCommand();
if (m_startNumber) {
m_displayField.setText(digit);
m_startNumber = false;
} else {
m_displayField.setText(m_displayField.getText() + digit);
}
}
}

class ClearListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
action_clear();
}
}
}

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);
}
}

-------------------------------

read for more information.

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