Revise paste LA PERT 4 - PBO

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

public class Form2 extends JFrame {
    public Form2(){

JPanel panel1 = new JPanel();
        JPanel panel2 = new JPanel();
        Container con = this.getContentPane();

final JRadioButton RB1 = new JRadioButton("Anggota Satu");
        final JRadioButton RB2 = new JRadioButton("Anggota Dua");
        final JRadioButton RB3 = new JRadioButton("Anggota Tiga");
        final JRadioButton RB4 = new JRadioButton("Anggota Empat");

ButtonGroup radioBgroup = new ButtonGroup();

final JLabel lblNPM   = new JLabel("NPM ");
        final JLabel lblNama  = new JLabel("Nama ");
        final JLabel lblJK    = new JLabel("Jenis Kelamin ");
        final JLabel lblKelas = new JLabel("Kelas ");

final JTextField txtNPM   = new JTextField(5);
        final JTextField txtNama  = new JTextField(5);
        final JTextField txtJK    = new JTextField(5);
        final JTextField txtKelas = new JTextField(5);
        final JButton cmdTampil   = new JButton("Tampil");
        final JButton cmdKosong   = new JButton("Kosongkan");
        final JButton cmdExit     = new JButton("Keluar");

con.setLayout(new GridLayout(1,2));
        panel1.setLayout(new GridLayout(3,3,2,5));
        panel2.setLayout(new GridLayout(6,3,2,5));
        panel1.setBorder(BorderFactory.createTitledBorder("Anggota"));
        panel2.setBorder(BorderFactory.createTitledBorder("Data"));

con.add(panel1);
        con.add(panel2);

radioBgroup.add(RB1);
        radioBgroup.add(RB2);
        radioBgroup.add(RB3);
        radioBgroup.add(RB4);

panel1.add(RB1);
        panel1.add(RB2);
        panel1.add(RB3);
        panel1.add(RB4);

panel2.add(lblNPM);
        panel2.add(txtNPM);
        panel2.add(lblNama);
        panel2.add(txtNama);
        panel2.add(lblJK);
        panel2.add(txtJK);
        panel2.add(lblKelas);
        panel2.add(txtKelas);
        panel2.add(cmdTampil);
        panel2.add(cmdKosong);
        panel2.add(cmdExit);

cmdTampil.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                if (RB1.isSelected()){
                    txtNPM.setText("50416855");
                    txtNama.setText("Anggi Alberto");
                    txtJK.setText("Laki - laki");
                    txtKelas.setText("2IA22");
                }

if (RB2.isSelected()){
                    txtNPM.setText("54214149");
                    txtNama.setText("Bella");
                    txtJK.setText("Perempuan");
                    txtKelas.setText("3IA22");
                }

if (RB3.isSelected()){
                    txtNPM.setText("51941520");
                    txtNama.setText("Aris");
                    txtJK.setText("Laki - laki");
                    txtKelas.setText("3IA22");
                }

if (RB4.isSelected()){
                    txtNPM.setText("53215265");
                    txtNama.setText("Najmi");
                    txtJK.setText("Perempuan");
                    txtKelas.setText("3IA18");
                }
            }
        });

cmdKosong.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                txtNPM.setText(" ");
                txtNama.setText(" ");
                txtJK.setText(" ");
                txtKelas.setText(" ");
                radioBgroup.clearSelection();
            }
        });

cmdExit.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                System.exit(0);
            }
        });

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setLocation(40,120);
        this.setSize(520,230);
        this.setVisible(true); 
    }

public static void main(String[] args) {
        new Form2();
    }
}