// CheckBoxDemoUsingItemEvent.java://    Extend ButtonDemo to add three check boxesimport java.awt.*;import java.awt.event.*;import javax.swing.*;public class CheckBoxDemoUsingItemEvent extends ButtonDemo  implements ItemListener {  // Create three check boxes to control the display of message  private JCheckBox jchkCentered = new JCheckBox("Centered");  private JCheckBox jchkBold = new JCheckBox("Bold");  private JCheckBox jchkItalic = new JCheckBox("Italic");  public static void main(String[] args) {    CheckBoxDemoUsingItemEvent frame =      new CheckBoxDemoUsingItemEvent();    frame.setTitle("CheckBoxDemoUsingItemEvent");    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    frame.setSize(500, 200);    frame.setVisible(true);  }  public CheckBoxDemoUsingItemEvent() {    // Set mnemonic keys    jchkCentered.setMnemonic('C');    jchkBold.setMnemonic('B');    jchkItalic.setMnemonic('I');    // Create a new panel to hold check boxes    JPanel jpCheckBoxes = new JPanel();    jpCheckBoxes.setLayout(new GridLayout(3, 0));    jpCheckBoxes.add(jchkCentered);    jpCheckBoxes.add(jchkBold);    jpCheckBoxes.add(jchkItalic);    getContentPane().add(jpCheckBoxes, BorderLayout.EAST);    // Register listeners with the check boxes    jchkCentered.addItemListener(this);    jchkBold.addItemListener(this);    jchkItalic.addItemListener(this);  }  /** Handle ItemEvent */  public void itemStateChanged(ItemEvent e) {    if (e.getSource() == jchkCentered) {      messagePanel.setCentered(jchkCentered.isSelected());    }    else if ((e.getSource() == jchkBold) ||      (e.getSource() == jchkItalic)) {      // Determine a font style      int fontStyle = Font.PLAIN;      fontStyle += (jchkBold.isSelected() ? Font.BOLD : 0);      fontStyle += (jchkItalic.isSelected() ? Font.ITALIC : 0);      // Set font for the message      Font font = messagePanel.getFont();      messagePanel.setFont(          new Font(font.getName(), fontStyle, font.getSize()));    }  }}