Java Applet - Calculate Celsius to Fahrenheit and Fahrenheit to Celsius Program

import java.awt.*;

import java.applet.*;

import java.awt.event.*;



public class change1 extends Applet

  {

    Button b1;

    TextField t1,t2,t3;

    Label l1,l2,l3,l4,l5;

    CheckboxGroup cg;

    Checkbox r1,r2;



public void init()

{  

       setLayout(null);

        l1 = new Label("Enter the Value : ");                 t1 = new TextField(10);

        l2 = new Label("Fahrenheit to Celsius is : ");    t2 = new TextField(10);

        l3 = new Label("Celsius to Fahrenheit is : ");     t3 = new TextField(10);

        cg=new CheckboxGroup();

        r1=new Checkbox("Fahrenheit to Celsius",cg,false);

        r2=new Checkbox("Celsius to Fahrenheit",cg,false);

        b1=new Button("Clear");



        l1.setBounds(170,50,100,25);                 t1.setBounds(280,50,100,25);

        r1.setBounds(100,100,125,25);              r2.setBounds(325,100,125,25); 

        l2.setBounds(150,150,130,25);               t2.setBounds(300,150,100,25);

        l3.setBounds(150,200,130,25);               t3.setBounds(300,200,100,25);

        b1.setBounds(230,250,100,25); 



            b1.addActionListener(new a());         r1.addItemListener(new aa());

            r2.addItemListener(new aa());

add(l1);  add(t1);  add(r1);  add(r2);  add(b1);  add(l2);  add(t2);  add(l3);  add(t3); 

}

class aa implements ItemListener

 { 

   double a1,a2,a3;

   public void itemStateChanged(ItemEventie)

   {  

         a1 = Double.parseDouble(t1.getText());

         if(ie.getSource()==r1)

            {    a2 = ( (a1-32) * 5) / 9;                  // check the value 222 = 105.556

                  t2.setText(String.valueOf(a2));           }

         if(ie.getSource()==r2)

           {     a3 = ( ((a1 * 9) / 5) +  32);            // check the value 37 = 98.6

                  t3.setText(String.valueOf(a3));           }

       }       

    }

class a implements ActionListener

 {

  public void actionPerformed(ActionEvent e)

     {

      if(e.getSource()==b1)

        {

            t1.setText("");

            t2.setText("");

            t3.setText("");   

         } 

       }

      }

  }



/* <applet code="change1.class"height=350 width=600>

</applet> */