7.4 Java1640 java oop anonymous classes

Revised: Wed May 11 15:54:45 CDT 2016

This page is included in the following Books:

• ITSE2317 - Java Programming (Intermediate)
• Object-Oriented Programming (OOP) with Java

Table of contents

• Preface
  • Purpose of this module
  • Viewing tip
    • Figures
    • Listings
• Preview
  • What can you include in a class definition?
  • What is an anonymous class?
  • What about an anonymous interface?
  • Why use anonymous classes?
  • Anonymous classes versus local classes
  • Restrictions on the use of anonymous classes
  • Smoke and mirrors
  • Syntax for anonymous classes
• Discussion and sample code
  • Class file names
  • Program structure and behavior
    • A local class
    • Three anonymous classes
    • The screen output
    • The controlling class
    • Local and anonymous classes inside GUI constructor
    • The GUI class
    • An anonymous inner class for low-level event handling
    • Instantiating and registering a MouseListener object
    • Extending the WindowAdapter class
  • The GUI remains on the screen until terminated
  • Simple event handlers
• Run the program
• Summary
• Miscellaneous
• Complete program listing
• Figures
• Listings

Preface

This module is one in a collection of modules designed for teaching ITSE2317 - Java Programming (Intermediate) at Austin Community College in Austin, TX.

(Editor's note: As you read this module, you will see that it was originally written around 2003. However, despite many improvements in Javasince then, most of what was true then is still true in 2013.)

This module makes several references to my website, which is located at (External Link) .

Purpose of this module

This module explains anonymous classes from a practical viewpoint, including a comparison between anonymous classes and local classes.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.

Figures

• Figure 1 . Syntax for anonymous classes.
• Figure 2 . Program GUI.
• Figure 3 . Class file names.
• Figure 4 . Screen output.
• Figure 5 . Screen output.
• Figure 6 . Screen output.
• Figure 7 . Screen output.
• Figure 8 . Screen output.
• Figure 9 . Screen output.

Listings

• Listing 1 . The controlling class.
• Listing 2 . Beginning of the GUI class.
• Listing 3 . Beginning of the BaldButton class.
• Listing 4 . The processMouseEvent method.
• Listing 5 . Beginning of anonymous inner class.
• Listing 6 . Overridden processMouseEvent method.
• Listing 7 . Register a MouseListener object.
• Listing 8 . Implementing the interface.
• Listing 9 . Registering a WindowListener on the Frame .
• Listing 10 . Complete program listing.

Preview

What can you include in a class definition ?

There are several different kinds of items that can be included in a class definition. As you learned in the earlier modules in this series, the listincludes:

• Static variables
• Instance variables
• Static methods
• Instance methods
• Constructors
• Static initializer blocks
• Instance initializers

Can also contain other class definitions

As you also learned in previous modules, a class definition can also contain the following kinds of inner classes: