//example 7-21
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class tt extends Applet implements ItemListener
{
   Checkbox c0,c1,c2;
   int i0,i1,i2;
   public void init()
   {
   	 c0=new Checkbox("0");
   	 c0.addItemListener(this);
   	 add(c0);
   	 c1=new Checkbox("1");
   	 c1.addItemListener(this);
   	 add(c1);
   	 c2=new Checkbox("2");
   	 c2.addItemListener(this);
   	 add(c2);
   }
   public void itemStateChanged(ItemEvent e)
   {
   	 i0=i1=i2=0;
   	 if(c0.getState())i0=1;
   	 if(c1.getState())i1=1;
   	 if(c2.getState())i2=1;
   	 repaint();
   }
   public void paint(Graphics g)
   {
   	 int k=i0+2*i1+4*i2;
   	 int c=25*k+10;
   	 Color co=new Color(c,c,c);
   	 g.setColor(co);
   	 g.fillRect(c,40,10,40);
   	 g.drawString(""+k,c,100);
   }
}