자바에서 지금 실행을 하면 계속 isSelected에서 걸리는데, 왜 그런지 모르겠어요.;;
뭐가 잘못된걸까요;.... 고수님들 지적 부탁드립니다.


import javax.swing.*;

import java.awt.event.*;
import java.awt.*;
import javax.swing.border.Border;
import javax.swing.border.TitledBorder;

class MyFrame extends JFrame  {
 

 private JLabel text = new JLabel ("");
 private JPanel topPanel, middlePanel, middle1Panel, middle2Panel, resultPanel;
 private JTextField name;
 private JButton save, cancel, quit;
 private JComboBox ClassList;
 private JRadioButton sex1, sex2 ,Grade1, Grade2, Grade3, Grade4;

 public MyFrame() {
  
  setTitle("실습");  
  topPanel = new JPanel();
  
  topPanel.add(new JLabel("성명"));
  name = new JTextField(10);
  topPanel.add(name,BorderLayout.WEST);
  
  String[] Class = {"컴퓨터공학부", "인터넷미미디어", "기계공학부", "정보통신공학부"};
  ClassList = new JComboBox(Class);
  ClassList.setSelectedIndex(0);
  topPanel.add(ClassList, BorderLayout.EAST);
  
  JRadioButton sex1 = new JRadioButton("남", true);
  JRadioButton sex2 = new JRadioButton("여");
  
  JRadioButton Grade1 = new JRadioButton("1학년", true);
  JRadioButton Grade2 = new JRadioButton("2");
  JRadioButton Grade3 = new JRadioButton("3");
  JRadioButton Grade4 = new JRadioButton("4");
  
  JPanel sizePanel = new JPanel();
  JPanel size2Panel = new JPanel();
  

  
  ButtonGroup group1 = new ButtonGroup();
  ButtonGroup group2 = new ButtonGroup();
  
  group1.add(sex1);
  group1.add(sex2);
  
  group2.add(Grade1);
  group2.add(Grade2); 
  group2.add(Grade3);
  group2.add(Grade4);
  
  sizePanel.add(sex1);
  sizePanel.add(sex2);
  
  size2Panel.add(Grade1);
  size2Panel.add(Grade2);
  size2Panel.add(Grade3);
  size2Panel.add(Grade4);
  
  Border sex = BorderFactory.createTitledBorder("성별");
  Border grade = BorderFactory.createTitledBorder("학년");
  
  sizePanel.setBorder(sex);
  size2Panel.setBorder(grade);
  
  middle1Panel = new JPanel();
  middle1Panel.add(sizePanel, BorderLayout.WEST);
  middle1Panel.add(size2Panel, BorderLayout.EAST);
  
  middle2Panel = new JPanel();  
  
  save = new JButton("저장");
  cancel = new JButton("취소");
  quit = new JButton("종료");
  
  save.addActionListener(new ButtonHandler());
  cancel.addActionListener(new ButtonHandler());
  quit.addActionListener(new ButtonHandler());
  
  middle2Panel.add(save,BorderLayout.WEST);
  middle2Panel.add(cancel,BorderLayout.CENTER);
  middle2Panel.add(quit,BorderLayout.EAST);
  
  middlePanel = new JPanel();
  
  middlePanel.add(middle1Panel,BorderLayout.SOUTH);
  middlePanel.add(middle2Panel,BorderLayout.NORTH);
  
  resultPanel = new JPanel();
  resultPanel.setBorder(new TitledBorder(""));
  resultPanel.add(text);
  
  add(topPanel,BorderLayout.NORTH);
  add(middlePanel, BorderLayout.CENTER);
  add(resultPanel, BorderLayout.SOUTH);
  
  setSize(350,300);
  setVisible(true);
  setResizable(false);  

  addWindowListener(new WindowHandler());  

 }
 class ButtonHandler implements ActionListener
 {
  public void actionPerformed(ActionEvent e)
  {
   JButton eventBtn = (JButton) e.getSource();

   if (eventBtn == save) // 메모 수정/수정완료 버튼을 누를 경우,
   {
    String Name = name.getText();
    String major = (String) ClassList.getSelectedItem();
    
    String sex;
    if(sex1.isSelected())
     sex = sex1.getText();
    else
     sex = sex2.getText();
    
    String grade;
    if(Grade1.isSelected())
     grade = Grade1.getText();
    else if(Grade2.isSelected())
     grade = Grade2.getText();
    else if(Grade3.isSelected())
     grade = Grade3.getText();
    else
     grade = Grade4.getText();

    text.setText(name + "은(는) " + major + " " + grade
      + "학년의 " + sex + "입니다.");
    name.setText("");
    sex1.setSelected(true);
    Grade1.setSelected(true);
    ClassList.setSelectedIndex(0);
    name.requestFocus();
   }
   else if (eventBtn == cancel)
   {
    text.setText("");
    name.setText("");
    sex1.setSelected(true);
    Grade1.setSelected(true);
    ClassList.setSelectedIndex(0);
    name.requestFocus();
   }
   else if (eventBtn == quit)
   {
    System.exit(0);
   }
  }
 }
}

public class JCH_2 extends JFrame {
 public static void main(String[] args) {
  new MyFrame();
 }
}
class WindowHandler extends WindowAdapter {
 public void windowClosing(WindowEvent e) {
  System.exit(0);
 }
}