JTabbedPane Prac

package shalYIT;
import javax.swing.*;
import java.awt.*;


public class JPaneDemo2 {
    JTabbedPane jtp;
    JTextField tf;
    JPanel jp;
    JFrame jf;
    JPaneDemo2(){
        jtp = new JTabbedPane();
        jtp.add("SIS", new JSisPanel());
        jtp.add("RADIO", new JColorPanel());
        jp = new JPanel();
        jp.setLayout(new FlowLayout());
        jp.add(jtp);
        jf = new JFrame();
        jf.getContentPane().add(jp);
        jf.setSize(400, 500);
        jf.setVisible(true);
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new JPaneDemo2();
    }

}

class JSisPanel extends JPanel{
    JComboBox<String> jc;
    JSisPanel(){
        jc = new JComboBox<String>();
        jc.addItem("abc");
        jc.addItem("def");
        jc.addItem("ghi");
        jc.addItem("jkl");
        jc.addItem("mno");
        add(jc);
    }
}

class JColorPanel extends JPanel{
    JRadioButton r1, r2, r3, r4;
    ButtonGroup bg;
    JColorPanel(){
        r1 = new JRadioButton("A");
        r2 = new JRadioButton("B");
        r3 = new JRadioButton("C");
        r4 = new JRadioButton("D");
        bg = new ButtonGroup();
        bg.add(r1);
        bg.add(r2);
        bg.add(r3);
        bg.add(r4);
        add(r1);add(r2);add(r3);add(r4);
    }
}