package testsystem;

import java.awt.*;
import java.awt.event.*;

public class Frame1 extends Frame implements  ActionListener
{
     static  Button bu=new Button("refresh");
     static Frame1  frm=new Frame1();
     static  Checkbox c1=new Checkbox("A");
     static Checkbox c2=new Checkbox("B");
     static Checkbox c3=new Checkbox("C");
     static Checkbox c4=new Checkbox("D");
     static  CheckboxGroup grp=new CheckboxGroup();


    public static void main(String args[])
    {


      c1.setCheckboxGroup(grp);
      c2.setCheckboxGroup(grp);
      c3.setCheckboxGroup(grp);
      c4.setCheckboxGroup(grp);
      frm.add(c1);
      frm.add(c2);
      frm.add(c3);
      frm.add(c4);
      frm.add(bu);
      bu.addActionListener(frm);
      frm.setLayout(new BorderLayout());
      frm.setSize(400,300);
      frm.setVisible(true);


    }
    public void actionPerformed(ActionEvent e)
    {
        Button btn=(Button)e.getSource();
        if(btn==bu)
        {
            c1.setState(false);
            c2.setState(false);
            c3.setState(false);
            c4.setState(false);
        }
    }
}