How to use Swing CheckBoxes

[Java Tip]

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JApplet;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class SwingCheckBoxes extends JApplet {
  private JTextArea t = new JTextArea(6, 15);

  private JCheckBox cb1 = new JCheckBox("Check Box 1"), cb2 = new JCheckBox(
      "Check Box 2"), cb3 = new JCheckBox("Check Box 3");

  public void init() {
    cb1.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        trace("1", cb1);
      }
    });
    cb2.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        trace("2", cb2);
      }
    });
    cb3.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        trace("3", cb3);
      }
    });
    Container cp = getContentPane();
    cp.setLayout(new FlowLayout());
    cp.add(new JScrollPane(t));
    cp.add(cb1);
    cp.add(cb2);
    cp.add(cb3);
  }

  private void trace(String b, JCheckBox cb) {
    if (cb.isSelected())
      t.append("Box " + b + " Set\n");
    else
      t.append("Box " + b + " Cleared\n");
  }

  public static void main(String[] args) {
    run(new SwingCheckBoxes(), 200, 200);
  }

  public static void run(JApplet applet, int width, int height) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(applet);
    frame.setSize(width, height);
    applet.init();
    applet.start();
    frame.setVisible(true);
  }
}