SwingでのJRadioButtonマルチセレクションボックスの使い方

import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
 
public class HK extends JFrame {
	JPanel jp=null;
	JRadioButton[] jb;
	JButton jt=new JButton("Submit");
    public HK()
    {
      jp=(JPanel)this.getContentPane();
      jp.setLayout(null); 
      jb=new JRadioButton[3];
      for(int i=0;i<3;i++)
      {
    	  jb[i]=new JRadioButton("jb"+(i+1)); 
      }
      for(int i=0;i<3;i++)
      {
    	  jb[i].setBounds(new Rectangle(20+60*i,20,60,25));
    	  jp.add(jb[i]);
      }
      jt.setBounds(new Rectangle(20,60,75,25));
      jp.add(jt);
      jt.addActionListener(new HK_bt_actionAdapter(this));
    }
	public static void main(String[] args) {
      HK frame=new HK();
      frame.setSize(400,200);
      frame.setVisible(true);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	 public void bt_actionPerformed(ActionEvent e) {
		 for(int i=0;i<3;i++)
		 {
			 if(jb[i].isSelected())// ,true ,false .
			 {
			   System.out.println(jb[i].getText());// 
			 }
		 }
	 } 
} 
class HK_bt_actionAdapter implements ActionListener {
	private HK adaptee;
	HK_bt_actionAdapter(HK adaptee) {
		this.adaptee = adaptee;
   }

	public void actionPerformed(ActionEvent e) {
		adaptee.bt_actionPerformed(e);
	}
}