A Practical Introduction Using BlueJ

Third Edition

David J. Barnes

Michael Kölling

The BlueJ revolution goes on! The third edition of Objects First with Java has been fully updated for Java 5.0, and features a new version of BlueJ providing even stronger support for learning Java syntax and semantics.

Hallmark features

• An ‘Objects First’ approach encourages students to exploit the power of OOP from the beginning
• A project-driven approach applies a problem-solving method to real applications.
• A CD-ROM containing the JDK and versions of BlueJ for a variety of operating systems
• A Companion Website at www.pearsoned.co.uk/barnes includes a style guide for all program examples, PowerPoint slides and other resources for both students and instructors.
• Additional resources can be found on the BlueJ website: www.bluej.org/objects-first/

New to the third edition

• Fully compliant with Java 5.0 features including generics
• A revised treatment of autobox and enumerators
• Expanded coverage of graphics and GUI programming
• A new version of the BlueJ environment, featuring:

  o Full support for Java 5.0

  o An all-new interface ‘look and feel’

  o A new ‘Code Pad’ feature, allowing immediate execution and evaluation of Java code.

About the Authors

David Barnes has 25 years experience in teaching programming. He and Michael Kölling both teach introductory Java courses at the Universityof Kent, Canterbury. Michael Kölling was a key member of the team that developed BlueJ at MonashUniversityin Australia.

[Copy to appear on inside front cover of 3rd edition]

From reviews of the original edition

“The book represents a valuable, new approach to introductory programming; it is still my best choice as textbook for the introductory programming course.”

—Michael Caspersen, University of Aarhus, Denmark

“This is the most innovative approach to teaching an Introduction to Programming course I have seen so far.”

—Clemens Martin, University of Ontario

“I would like to thank the authors for their good job on this book, and the wonderful BlueJ, the best programming environment for students learning Java.”

—Ying Zhou, Rhode Island College

The first true ‘objects first’ introductory text; the best introduction to objects and OO programming concepts I have ever seen.”

—Michael Goldweber, XavierUniversity

“The more I read Barnes and Kölling’s book, the more impressed I am with it. It is a pedagogical masterpiece.”

—Ian Bridgewood, CopenhagenUniversityCollegeof Engineering

Foreword

Preface to the instructor

List of projects discussed in detail in this book

Acknowledgements

Part 1 Foundations of object orientation

Chapter 1 Objects and classes

1.1 Objects and classes

1.2 Creating objects

1.3 Calling methods

1.4 Parameters

1.5 Data types

1.6 Multiple instances

1.7 State

1.8 What is in an object?

1.9 Object interaction

1.10 Source code

1.11 Another example

1.12 Return values

1.13 Objects as parameters

1.14 Summary

Chapter 2 Understanding class definitions

2.1 Ticket machines

2.1.1 Exploring the behavior of a naïve ticket machine

2.2 Examining a class definition

2.3 Fields, constructors, and methods

2.3.1 Fields

2.3.2 Constructors

2.4 Passing data via parameters

2.5 Assignment

2.6 Accessor methods  

2.7 Mutator methods

2.8 Printing from methods  

2.9 Summary of the naïve ticket machine

2.10 Reflecting on the design of the ticket machine

2.11 Making choices: the conditional statement

2.12 A further conditional-statement example

2.13 Local variables

2.14 Fields, parameters, and local variables

2.15 Summary of the better ticket machine

2.16 Self-review exercises

2.17 Reviewing a familiar example

2.18 Summary

Chapter 3 Object interaction

3.1 The clock example

3.2 Abstraction and modularization

3.3 Abstraction in software

3.4 Modularization in the clock example

3.5 Implementing the clock display

3.6 Class diagrams versus object diagrams

3.7 Primitive types and object types

3.8 The ClockDisplay source code

3.8.1 Class NumberDisplay

3.8.2 String concatenation

3.8.3 The modulo operator

3.8.4 Class ClockDisplay

3.9 Objects creating objects

3.10 Multiple constructors

3.11 Method calls

3.11.1 Internal method calls

3.11.2 External method calls

3.11.3 Summary of the clock display

3.12 Another example of object interaction

3.12.1 The mail system example

3.12.2 The this keyword

3.13 Using a debugger

3.13.1 Setting breakpoints

3.13.2 Single stepping 

3.13.3 Stepping into methods

3.14 Method calling revisited

3.15 Summary

Chapter 4 Grouping objects

4.1 Grouping objects in flexible-size collections

4.2 A personal notebook

4.3 A first look at library classes

4.3.1 An example of using a library 

4.4 Object structures with collections

4.5 Generic classes

4.6 Numbering within collections

4.7 Removing an item from a collection

4.8 Processing a whole collection

4.8.1 The for-each loop

4.8.2 The while loop

4.8.3 Iterating over a collection

4.8.4 Index access versus iterators

4.9 Summary of the notebook example

4.10 Another example: an auction system

4.10.1 The Lot class

4.10.2 The Auction class

4.10.3 Anonymous objects

4.10.4 Using collections

4.11 Flexible collection summary

4.12 Fixed-size collections

4.12.1 A log-file analyzer

4.12.2 Declaring array variables

4.12.3 Creating array objects

4.12.4 Using array objects

4.12.5 Analyzing the log file

4.12.6 The for loop

4.13 Summary

Chapter 5 More sophisticated behavior

5.1 Documentation for library classes

5.2 The TechSupport system

5.2.1 Exploring the TechSupport system

5.2.2 Reading the code

5.3 Reading class documentation

5.3.1 Interfaces versus implementation

5.3.2 Using library-class methods

5.3.3 Checking string equality

5.4 Adding random behavior

5.4.1 The Random class

5.4.2 Random numbers with limited range

5.4.3 Generating random responses

5.4.4 Reading documentation for parameterized classes

5.5 Packages and import

5.6 Using maps for associations

5.6.1 The concept of a map

5.6.2 Using a HashMap

5.6.3 Using a map for the TechSupport system

5.7 Using sets

5.8 Dividing strings

5.9 Finishing the TechSupport system

5.10 Writing class documentation

5.10.1 Using javadoc in BlueJ

5.10.2 Elements of class documentation

5.11 Public versus private

5.11.1 Information hiding

5.11.2 Private methods and public fields

5.12 Learning about classes from their interfaces

5.13 Class variables and constants

5.13.1 The static key word

5.13.2 Constants

5.14 Summary

Chapter 6 Well-behaved objects

6.1 Introduction

6.2 Testing and debugging

6.3 Unit testing within BlueJ

6.3.1 Using inspectors

6.3.2 Positive versus negative testing

6.4 Test automation

6.4.1 Regression testing

6.4.2 Automated checking of test results

6.4.3 Recording a test

6.4.4 Fixtures

6.5 Modularization and interfaces

6.6 A debugging scenario

6.7 Commenting and style

6.8 Manual walkthroughs

6.8.1 A high-level walkthrough

6.8.2 Checking state with a walkthrough

6.8.3 Verbal walkthroughs

6.9 Print statements

6.9.1 Turning debugging information on or off

6.10 Choosing a test strategy

6.11 Debuggers

6.12 Putting the techniques into practice

6.13 Summary

Chapter 7 Designing classes

7.1 Introduction

7.2 The world-of-zuul game example

7.3 Introduction to coupling and cohesion

7.4 Code duplication

7.5 Making extensions

7.5.1 The task

7.5.2 Finding the relevant source code

7.6 Coupling

7.6.1 Using encapsulation to reduce coupling

7.7 Responsibility-driven design

7.7.1 Responsibilities and coupling

7.8 Localizing change

7.9 Implicit coupling

7.10 Thinking ahead

7.11 Cohesion

7.11.1 Cohesion of methods

7.11.2 Cohesion of classes

7.11.3 Cohesion for readability

7.11.4 Cohesion for reuse

7.12 Refactoring

7.12.1 Refactoring and testing

7.12.2 An example of refactoring

7.13 Refactoring for language independence

7.13.1 Enumerated types

7.13.2 Further decoupling of the command interface

7.14 Design guidelines

7.15 Executing without BlueJ

7.15.1 Class methods

7.15.2 The main method

7.15.3 Limitations of class methods

7.16 Summary

Part 2 Application structures

Chapter 8 Improving structure with inheritance

8.1 The DoME example

8.1.1 DoME classes and objects

8.1.2 DoME source code

8.1.3 Discussion of the DoME application

8.2 Using inheritance

8.3 Inheritance hierarchies

8.4 Inheritance in Java

8.4.1 Inheritance and access rights

8.4.2 Inheritance and initialization

8.5 DoME: adding other item types

8.6 Advantages of inheritance (so far)

8.7 Subtyping

8.7.1 Subclasses and subtypes

8.7.2 Subtyping and assignment

8.7.3 Subtyping and parameter passing

8.7.4 Polymorphic variables

8.7.5 Casting

8.8 The Object class

8.9 Autoboxing and Wrapper classes

8.10 The collection hierarchy

8.11 Summary

Chapter 9 More about inheritance

9.1 The problem: DoME’s print method

9.2 Static type and dynamic type

9.2.1 Calling print from Database

9.3 Overriding

9.4 Dynamic method lookup

9.5 Super call in methods

9.6 Method polymorphism

9.7 Object methods: toString

9.8 Protected access

9.9 Another example of inheritance with overriding

9.10 Summary

Chapter 10 Further abstraction techniques

10.1 Simulations

10.2 The foxes-and-rabbits simulation

10.2.1 The foxes-and-rabbits project

10.2.2 The Rabbit class

10.2.3 The Fox class

10.2.4 The Simulator class: setup

10.2.5 The Simulator class: a simulation step

10.2.6 Taking steps to improve the simulation

10.3 Abstract classes

10.3.1 The Animal superclass

10.3.2 Abstract methods

10.3.3 Abstract classes

10.4 More abstract methods

10.5 Multiple inheritance

10.5.1 An Actor class

10.5.2 Flexibility through abstraction

10.5.3 Selective drawing

10.5.4 Drawable actors: multiple inheritance

10.6 Interfaces

10.6.1 An Actor interface

10.6.2 Multiple inheritance of interfaces

10.6.3 Interfaces as types

10.6.4 Interfaces as specifications

10.6.5 A further example of interfaces

10.6.6 Abstract class or interface?

10.7 Summary of inheritance

10.8 Summary

Chapter 11 Building graphical user interfaces

11.1 Introduction

11.2 Components, layout, and event handling

11.3 AWT and Swing

11.4 The ImageViewer example

11.4.1 First experiments: creating a frame

11.4.2 Adding simple components

11.4.3 Adding menus

11.4.4 Event handling

11.4.5 Centralized receipt of events

11.4.6 Inner classes

11.4.7 Anonymous inner classes

11.5 ImageViewer 1.0: the first complete version

11.5.1 Image-processing classes

11.5.2 Adding the image

11.5.3 Layout

11.5.4 Nested containers

11.5.5 Image filters

11.5.6 Dialogs

11.6 ImageViewer 2.0: improving program structure

11.7 ImageViewer 3.0: more interface components

11.7.1 Buttons

11.7.2 Borders

11.8 Further extensions

11.9 Another example: SoundPlayer338

11.10 Summary

Chapter 12 Handling errors

12.1 The address-book project

12.2 Defensive programming

12.2.1 Client–server interaction

12.2.2 Argument checking

12.3 Server error reporting

12.3.1 Notifying the user

12.3.2 Notifying the client object

12.4 Exception-throwing principles

12.4.1 Throwing an exception

12.4.2 Exception classes

12.4.3 The effect of an exception

12.4.4 Unchecked exceptions

12.4.5 Preventing object creation

12.5 Exception handling

12.5.1 Checked exceptions: the throws clause

12.5.2 Catching exceptions: the try statement

12.5.3 Throwing and catching multiple exceptions

12.5.4 Propagating an exception

12.5.5 The finally clause

12.6 Defining new exception classes

12.7 Using assertions

12.7.1 Internal consistency checks

12.7.2 The assert statement

12.7.3 Guidelines for using assertions

12.7.4 Assertions and the BlueJ unit testing framework

12.8 Error recovery and avoidance

12.8.1 Error recovery

12.8.2 Error avoidance

12.9 Case study: text input/output

12.9.1 Readers, writers, and streams

12.9.2 The address-book-io project

12.9.3 Text output with FileWriter

12.9.4 Text input with FileReader

12.9.5 Scanner: reading input from the terminal

12.9.6 Object serialization

12.10 Summary

Chapter 13 Designing applications

13.1 Analysis and design

13.1.1 The verb/noun method

13.1.2 The cinema booking example

13.1.3 Discovering classes

13.1.4 Using CRC cards

13.1.5 Scenarios

13.2 Class design

13.2.1 Designing class interfaces

13.2.2 User interface design

13.3 Documentation

13.4 Cooperation

13.5 Prototyping

13.6 Software growth

13.6.1 Waterfall model

13.6.2 Iterative development

13.7 Using design patterns

13.7.1 Structure of a pattern

13.7.2 Decorator

13.7.3 Singleton

13.7.4 Factory method

13.7.5 Observer

13.7.6 Pattern summary

13.8 Summary

Chapter 14 A case study

14.1 The case study

14.1.1 The problem description

14.2 Analysis and design

14.2.1 Discovering classes

14.2.2 Using CRC cards

14.2.3 Scenarios

14.3 Class design

14.3.1 Designing class interfaces

14.3.2 Collaborators

14.3.3 The outline implementation

14.3.4 Testing

14.3.5 Some remaining issues

14.4 Iterative development

14.4.1 Development steps

14.4.2 A first stage

14.4.3 Testing the first stage

14.4.4 A later stage of development

14.4.5 Further ideas for development

14.4.6 Reuse

14.5 Another example

14.6 Taking things further

Appendices

A Working with a BlueJ project

B Java data types

C Java control structures

D Operators

E Running Java without BlueJ

F Configuring BlueJ

G Using the debugger

H JUnit unit-testing tools

I Javadoc

J Program style guide

K Important library classes

Index