Event Handling

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




public class Calculator extends JFrame
{
JLabel lblNumber=new JLabel("Number");
JLabel lblSquareRoot=new JLabel("Square Root");
JLabel lblCubicRoot=new JLabel("Cuboc Root");
JLabel lblRound=new JLabel("Round");

JTextField txtNumber=new JTextField();
JTextField txtSquareRoot=new JTextField();
JTextField txtCubicRoot=new JTextField();
JTextField txtRound=new JTextField();

JButton btnClose=new JButton("Close");
JButton btnClear=new JButton("Clear");


public Calculator()
{
Container c=getContentPane();
c.setLayout(new GridLayout(0,2));
c.add(lblNumber);
c.add(txtNumber);
c.add(lblSquareRoot);
c.add(txtSquareRoot);
c.add(lblCubicRoot);
c.add(txtCubicRoot);
c.add(lblRound);
c.add(txtRound);
c.add(btnClose);
c.add(btnClear);

pack();
setVisible(true);


txtNumber.addKeyListener(new KeyListener()
{
public void keyReleased(KeyEvent ke);
{
double number=Double.parseDouble(txtNumber.getText());
txtSquareRoot.setText(""+Math.sqrt(number));
txtCubicRoot.setText(""+Math.cbrt(number));
txtRound.setText(""+Math.round(number));
}


public void keyPressed(KeyEvent ke);
{

}


public void keyTyped(KeyEvent ke);
{

}
});




btnClose.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae);
{
System.exit(0);
}
});







btnClear.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae);
{
txtNumber.setText("");
txtSquareRoot.setText("");
txtCubicRoot.setText("");
txtRound.setText("");
}
});


txtSquareRoot.setEditable(false);
txtCubicRoot.setEditable(false);
txtRound.setEditable(false);
}



public static void main(String args[])
{
Calculator calculator=new Calculator();
}
}