RadioButton ItemListener

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

class Radiobutton extends JFrame implements ItemListener
{
    JRadioButton first,second,third,fourth;
    JPanel p1,p2,p3,p4;
    Container conn;
 
    Radiobutton()
    {    
        conn=getContentPane();
        conn.setBackground(Color.ORANGE);
   
        p1=new JPanel();
        p1.setBackground(Color.blue);
   
        p2=new JPanel();
        p2.setBackground(Color.red);
   
        p3=new JPanel();
        p3.setBackground(Color.black);
   
        p4=new JPanel();
        p4.setBackground(Color.yellow);
   
   
        first = new JRadioButton("Blue");
        second = new JRadioButton("red");
        third = new JRadioButton("Black");
        fourth = new JRadioButton("Yellow");
 
    
        //Add on Frame
        conn.add(first);conn.add(second);conn.add(third);conn.add(fourth);
  
  
        ButtonGroup bg = new ButtonGroup();
        bg.add(first);bg.add(second);bg.add(third);bg.add(fourth);
  
        first.addItemListener(this);
        second.addItemListener(this);
        third.addItemListener(this);
        fourth.addItemListener(this);
  
    }
 
    public void itemStateChanged(ItemEvent e )
    {
        if (first.isSelected()) 
        {
            conn.add(p1);
            conn.remove(p2);conn.remove(p3);conn.remove(p4);
            p1.setBounds(40,60,30,30);
            this.repaint();
    
        }
        if (second.isSelected()) 
        {
            conn.add(p2);
            conn.remove(p1);conn.remove(p3);conn.remove(p4);
            p2.setBounds(100,60,30,30);
            this.repaint();
        }
        if (third.isSelected()) 
        {
            conn.add(p3);
            conn.remove(p2);conn.remove(p1);conn.remove(p4);
            p3.setBounds(160,60,30,30);
            this.repaint();
        }
        if (fourth.isSelected()) 
        {
            conn.add(p4);
            conn.remove(p2);conn.remove(p3);conn.remove(p1);
            p4.setBounds(220,60,30,30);
            this.repaint();
        }
   
    } 
    public static void main(String[] args) 
    {
        JFrame win = new Radiobutton();
  
        win.setTitle("Radiobutton");
        win.setSize(300,200);
        win.setLayout(new FlowLayout());
        win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        win.setVisible(true);
    }  
}

Output