import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import javax.swing.*;
 
public class QuizFourBib extends JDialog {
        List<Question> questions = new ArrayList<Question>();
        int score=0;
        ButtonGroup group = new ButtonGroup();
        JButton btnOk = new JButton("Ok");
 
        public QuizFourBib(){
            super();
            setModal(true);
            setLayout(new BoxLayout(getContentPane(),BoxLayout.Y_AXIS));
            btnOk.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                    setVisible(false);
                }
            });
 
            questions.add(new Question("Who killed Goliath?", new String[]{"David", "Saul"}, "David"));
            questions.add(new Question("Where was Moses born?", new String[]{"Egypt","Samaria"}, "Egypt"));
        }
 
        public int startQuiz(){
            int score=0;
            for (Question q : questions){
                displayQuestion(q);
                if (group.getSelection().getActionCommand().equals(q.getCorrectAnswer())){
                    score++;
                }
            }
            dispose();
            return score;
        }
 
        private void displayQuestion(Question q){
            getContentPane().removeAll();
            for (Enumeration buttonGroup=group.getElements(); buttonGroup.hasMoreElements(); ){
                group.remove((AbstractButton)buttonGroup.nextElement());
            }
 
            JLabel questionText = new JLabel(q.getQuestion());
            getContentPane().add(questionText);
            for (String answer : q.getAnswers()){
                JRadioButton radio = new JRadioButton(answer);
                radio.setActionCommand(answer);
                group.add(radio);
                getContentPane().add(radio);
            }
            getContentPane().add(btnOk);
            pack();
            setVisible(true);
        }
 
    public static void main(String args[]) {
        QuizFourBib quiz = new QuizFourBib();
        int score = quiz.startQuiz();
 
        JOptionPane.showMessageDialog(null,"Your score: "+score,"",JOptionPane.INFORMATION_MESSAGE); 
    }
 
    class Question {
        String question="";
        String[] answers;
        String correctAnswer;
 
        public Question(String question, String[] possibleAnswers, String correctAnswer){
            this.question = question;
            this.answers = possibleAnswers;
            this.correctAnswer = correctAnswer;
        }
 
        public String getQuestion() {
            return question;
        }
 
        public String[] getAnswers() {
            return answers;
        }
 
        public String getCorrectAnswer() {
            return correctAnswer;
        }
    }
 
}

if (group.getSelection()!=null && group.getSelection().getActionCommand().equals(q.getCorrectAnswer())){