Java Programming Tutorial - 66, 67 - JRadioButton

import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JRadioButton;
import javax.swing.ButtonGroup;

class RadioButtons {
   public static void main(String args[ ]) {
      Gui gui = new Gui();
      gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      gui.setSize(320, 100);
      gui.setVisible(true);
   }
}

class Gui extends JFrame {
   private JTextField text;
   private JRadioButton plain, bold, italic, boldItalic;
   private Font plainFont, boldFont, italicFont, boldItalicFont;

   Gui() {
      super("My radio buttons");
      setLayout(new FlowLayout());

      plainFont = new Font("Serif", Font.PLAIN, 14);
      boldFont = new Font("Serif", Font.BOLD, 14);
      italicFont = new Font("Serif", Font.ITALIC, 14);
      boldItalicFont = new Font("Serif", Font.BOLD + Font.ITALIC, 14);

      text = new JTextField("This my super awesome sentence.", 23);
      text.setFont(plainFont);
      plain = new JRadioButton("Plain", true);
      bold = new JRadioButton("Bold", false);
      italic = new JRadioButton("Italic", false);
      boldItalic = new JRadioButton("Bold and italic", false);
      add(text);
      add(plain);
      add(bold);
      add(italic);
      add(boldItalic);

      ButtonGroup gr = new ButtonGroup();
      gr.add(plain);
      gr.add(bold);
      gr.add(italic);
      gr.add(boldItalic);

      plain.addItemListener(new handler(plainFont));
      bold.addItemListener(new handler(boldFont));
      italic.addItemListener(new handler(italicFont));
      boldItalic.addItemListener(new handler(boldItalicFont));
   }

   private class handler implements ItemListener {
      Font font;

      handler(Font f) {
         font = f;
      }

      public void itemStateChanged(ItemEvent event) {
         text.setFont(font);
      }
   }

}