Factorial program using swings

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

class Factorial extends JFrame {
JTextField t1, t2;

Factorial() {
JLabel l1 = new JLabel("Enter Number: ");
JLabel l2 = new JLabel("Factorial of Input Number: ");
t1 = new JTextField(20);
t2 = new JTextField(20);
JPanel p = new JPanel(new GridLayout(3, 2));
JButton b = new JButton("Find");
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String number = t1.getText();
int num = Integer.parseInt(number);
long fac = num;
for (int i = num; i > 1; i--) {
fac = fac * (i - 1);
}
t2.setText(Long.toString(fac));

}
});
p.add(l1);
p.add(t1);
p.add(l2);
p.add(t2);
p.add(b);
add(p);
setVisible(true);
pack();
}

public static void main(String[] args) {
Factorial f = new Factorial();
}
}


OUTPUT: