Factorial Evaluation Using Applets

import java.applet.*;
import java.awt.event.*;
import java.awt.*;
/*<applet code="App2.class" height=600 width=600>
</applet>*/
public class App2 extends Applet implements ActionListener
{
 TextField t1,t2;
 Button b;
 Label l1,l2;
 int a,fact;
 public void init()
 { l1=new Label("Enter a number",Label.LEFT);
  l2=new Label("Result",Label.RIGHT);
  t1=new TextField(5);
  t2=new TextField(10);
  b=new Button("Compute");
  add(l1);
  add(t1);
  add(l2);
  add(t2);
  add(b);
  b.addActionListener(this);
 }
 public void actionPerformed(ActionEvent ae)
 { a=Integer.parseInt(t1.getText());
  fact=1;
  if(a<0)
  {
   t2.setText("Wrong input");
  }
  else
  {
   for(int i=a;i>1;i--)
    fact*=i;
  }
  t2.setText(""+fact);
  //repaint();
 }
}