CheckBox ItemListener

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

class CheckBox extends JFrame implements ItemListener
{
    JCheckBox ch1,ch2;
    JPanel p1,p2;
    Container conn;
 
    CheckBox()
    {    
        conn=getContentPane();
        conn.setBackground(Color.WHITE);
   
        p1=new JPanel();p1.setBackground(Color.yellow);   
        p2=new JPanel();p2.setBackground(Color.red);   
     
        ch1=new JCheckBox("Blue",false);ch1.setOpaque(false);
        ch2=new JCheckBox("Red",false);ch2.setOpaque(false);

        conn.add(ch1);conn.add(ch2);
  
        ch1.addItemListener(this);ch2.addItemListener(this);
  
    }
 
    public void itemStateChanged(ItemEvent e )
    {
        if (ch1.isSelected()==true) 
        {
            conn.add(p1);p1.setBounds(30,40,50,30);
            this.repaint();    
        }
        if(ch1.isSelected()==false) 
        {
            conn.remove(p1);p1.setBounds(30,40,50,30);
            this.repaint();    
        }
        if (ch2.isSelected()==true) 
        {
            conn.add(p2);p2.setBounds(100,40,50,30);
            this.repaint();
        }
   if (ch2.isSelected()==false) 
        {
            conn.remove(p2);p2.setBounds(100,40,50,30);
            this.repaint();
        }
    } 
  
    public static void main(String[] args) 
    {
        JFrame win = new CheckBox();
        win.setTitle("CheckBox");
        win.setSize(200,120);
        win.setLayout(new FlowLayout());
        win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        win.setVisible(true);
    }  
}

Output