Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

612 Chapter 16 Event-Driven Programming
✓Point✓ Check
16.9 If class A is an inner class in class B, what is the .class file for A? If class B contains
two anonymous inner classes, what are the .class file names for these two classes?
16.10 What is wrong in the following code?
import java.swing.*;
import java.awt.*;
public class Test extends JFrame {
public Test() {
JButton jbtOK = new JButton("OK");
add(jbtOK);
}
}
private class Listener
implements ActionListener {
public void actionPerform
(ActionEvent e) {
System.out.println
(jbtOK.getActionCommand());
}
}
/** Main method omitted */
(a)
import java.awt.event.*;
import javax.swing.*;
public class Test extends JFrame {
public Test() {
JButton jbtOK = new JButton("OK");
add(jbtOK);
jbtOK.addActionListener(
new ActionListener() {
public void actionPerformed
(ActionEvent e) {
System.out.println
(jbtOK.getActionCommand());
}
} // Something missing here
}
}
/** Main method omitted */
(b)
16.11 What is the difference between the setSize(width, height) method and the
pack() method in JFrame?
Key
Point
16.6 Alternative Ways of Defining Listener Classes
Using an inner class or an anonymous inner class is preferred for defining listener
classes.
There are many other ways to define the listener classes. For example, you can rewrite Listing
16.4 by creating just one listener, register the listener with the buttons, and let the listener
detect the event source—that is, which button fires the event—as shown in Listing 16.5.
LISTING 16.5
DetectSourceDemo.java
1 import javax.swing.*;
2 import java.awt.event.*;
3
4 public class DetectSourceDemo extends JFrame {
5 // Create four buttons
6 private JButton jbtNew = new JButton("New");
7 private JButton jbtOpen = new JButton("Open");
8 private JButton jbtSave = new JButton("Save");
9 private JButton jbtPrint = new JButton("Print");
10
11 public DetectSourceDemo() {
12 // Create a panel to hold buttons
13 JPanel panel = new JPanel();
14 panel.add(jbtNew);
15 panel.add(jbtOpen);
16 panel.add(jbtSave);
17 panel.add(jbtPrint);
18