The Object-Oriented Thought Process / Edition 4

by Matt Weisfeld

Overview

The Object-Oriented Thought Process, Second Edition will lay the foundation in object-oriented concepts and then explain how various object technologies are used. Author Matt Weisfeld introduces object-oriented concepts, then covers abstraction, public and private classes, reusing code, and devloping frameworks. Later chapters cover building objects that work with XML, databases, and distributed systems (including EJBs, .NET, Web Services and more).Throughout the book Matt uses UML, the standard language for modeling objects, to provide illustration and examples of each concept.

Product Details

ISBN-13:	9780321861276
Publisher:	Pearson Education
Publication date:	03/13/2013
Series:	Developer's Library
Edition description:	Older Edition
Pages:	336
Product dimensions:	6.90(w) x 8.90(h) x 0.90(d)

About the Author

Matt Weisfeld is a college professor, software developer, and author based in Cleveland, Ohio. Prior to teaching college full time, he spent 20 years in the information technology industry as a software developer, entrepreneur, and adjunct professor. Weisfeld holds an MS in computer science and an MBA. Besides the first three editions of The Object-Oriented Thought Process, he has authored two other software development books and published many articles in magazines and journals, such as developer.com, Dr. Dobb’s Journal, The C/C++ Users Journal, Software Development Magazine, Java Report, and the international journal Project Management.

Read an Excerpt

IntroductionIntroductionThis Book's Scope

As the title indicates, this book is about the object-oriented (OO) thought process. Obviously, choosing the theme and title of the book are important decisions; however, these decisions were not all that simple. Numerous books deal with various levels of object orientation. Several popular books deal with topics including OO analysis, OO design, OO programming, design patterns, OO data (

However, while pouring over all of these books, many people forget that all of these topics are built on a single foundation: how you think in OO ways. It is unfortunate, but software professionals often dive into these books without taking the appropriate time and effort to really understand the concepts behind the content.

I contend that learning OO concepts is not accomplished by learning a specific development method or a set of tools. Doing things in an OO manner is, simply put, a way of thinking. This book is all about the OO thought process.

Separating the methods and tools from the OO thought process is not easy. Many people are introduced to OO concepts via one of these methods or tools. For example, years ago, most C programmers were first introduced to object orientation by migrating directly to C++—before they were even remotely exposed to OO concepts. Other software professionals were first introduced to object orientation by presentations that included object models using UML—again, before they were even exposed directly to OO concepts. It is not unusual to find that programming books and courses defer OO concepts until later in the learning process.

It is important to understand the significantdifference between learning OO concepts and using the methods and tools that support the paradigm. This came into focus for me before I worked on the first edition of this book when I read articles such as Craig Larman's "What the UML Is—and Isn't," In this article he states,

Unfortunately, in the context of software engineering and the UML diagramming language, acquiring the skills to read and write UML notation seems to sometimes be equated with skill in object-oriented analysis and design. Of course, this is not so, and the latter is much more important than the former. Therefore, I recommend seeking education and educational materials in which intellectual skill in object-oriented analysis and design is paramount rather than UML notation or the use of a case tool.

Although learning a modeling language is an important step, it is much more important to learn OO skills first. Learning UML before OO concepts is similar to learning how to read an electrical diagram without first knowing anything about electricity.

The same problem occurs with programming languages. As stated earlier, many C programmers moved into the realm of object orientation by migrating to C++ before being directly exposed to OO concepts. This would always come out in an interview. Many times developers who claim to be C++ programmers are simply C programmers using C++ compilers. Even now, with languages such as C# .NET, VB .NET, and Java well established, a few key questions in a job interview can quickly uncover a lack of OO understanding.

Early versions of Visual Basic are not OO. C is not OO, and C++ was developed to be backward compatible with C. Because of this, it is quite possible to use a C++ compiler (writing only C syntax) while forsaking all of C++'s OO features. Even worse, a programmer can use just enough OO features to make a program incomprehensible to OO and non-OO programmers alike.

Thus, it is of vital importance that while you're on the road to OO development, you first learn the fundamental OO concepts. Resist the temptation to jump directly into a programming language (such as VB .NET, C++, C# .NET or Java) or a modeling language (such as UML), and take the time to learn the object-oriented thought process.

In my first class in Smalltalk in the late 1980s, the instructor told the class that the new OO paradigm was a totally new way of thinking (despite the fact that it has been around since the 60s). He went on to say that although all of us were most likely very good programmers, about 10%–20% of us would never really grasp the OO way of doing things. If this statement is indeed true, it is most likely because some people never really take the time to make the paradigm shift and learn the underlying OO concepts.What's New in the Third Edition

As stated often in this introduction, my vision for the first edition was primarily a conceptual book. Although I still adhere to this goal for the second and third editions, I have included several application topics that fit well with object-oriented concepts. For the third edition I expand on many of the topics of the second edition and well as include totally new chapters. These revised and updated concepts

• Object persistence and serialization.

• Adding properties to attributes.

• Client/Server technologies.

• Expanded code examples in Java, C# .NET and VB .NET.

The chapters that cover these topics are still conceptual in nature; however, many of the chapters include Java code that shows how these concepts are implemented. In this third edition, a code appendix is included that presents the chapter's examples in C# .NET and Visual Basic .NET.The Intended Audience

This book is a general introduction to fundamental OO concepts with code examples to reinforce the concepts. One of the most difficult juggling acts was to keep the material conceptual while still providing a solid, technical code base. The goal of this book is to allow a reader to understand the concepts and technology without having a compiler at hand. However, if you do have a compiler available, then there is code to be investigated.

The intended audience includes business managers, designers, developers, programmers, project managers, and anyone who wants to gain a general understanding of what object orientation is all about. Reading this book should provide a strong foundation for moving to other books covering more advanced OO topics.

Of these more advanced books, one of my favorites remains Object-Oriented Design in Java by Stephen Gilbert and Bill McCarty. I really like the approach of the book, and have used it as a textbook in classes I have taught on OO concepts. I cite Object-Oriented Design in Java often throughout this book, and I recommend that you graduate to it after you complete this one.

Other books that I have found very helpful include Effective C++ by Scott Meyers, Classical and Object-Oriented Software Engineering by Stephen R. Schach, Thinking in C++ by Bruce Eckel, UML Distilled by Martin Flower, and Java Design by Peter Coad and Mark Mayfield.

The conceptual nature of this book provides a unique perspective in regards to other computer technology books. While books that focus on specific technologies, such as programming languages, struggle with the pace of change, this book has the luxury of presenting established concepts that, while certainly being fine-tuned, do not experience radical changes. With this in mind, many of the books that were referenced several years ago, are still referenced because the concepts are still fundamentally the same.This Book's Scope

It should be obvious by now that I am a firm believer in becoming comfortable with the object-oriented thought process before jumping into a programming language or modeling language. This book is filled with examples of code and UML diagrams; however, you do not need to know a specific programming language or UML to read it. After all I have said about learning the concepts first, why is there so much Java, C# .NET, and VB .NET code and so many UML diagrams? First, they are all great for illustrating OO concepts. Second, both are vital to the OO process and should be addressed at an introductory level. The key is not to focus on Java, C# .NET, and VB .NET or UML, but to use them as aids in the understanding of the underlying concepts.

The Java, C# .NET and VB .NET examples in the book illustrate concepts such as loops and functions. However, understanding the code itself is not a prerequisite for understanding the concepts; it might be helpful to have a book at hand that covers specific languages syntax if you want to get more detailed.

I cannot state too strongly that this book does not teach Java, C# .NET, and VB .NET or UML, all of which can command volumes unto themselves. It is my hope that this book will whet your appetite for other OO topics, such as OO analysis, object-oriented design, and OO programming.This Book's Conventions

The following conventions are used in this book:

• Code lines, commands, statements, and any other code-related terms appear in a monospace typeface.

• Placeholders that stand for what you should actually type appear in italic monospace. Text that you should type appears in bold monospace.

• Throughout the book, there are special sidebar elements, such as

***

Note - A Note presents interesting information related to the discussion—a little more insight or a pointer to some new technique.

***

***

Tip - A Tip offers advice or shows you an easier way of doing something.

***

***

Caution - A Caution alerts you to a possible problem and gives you advice on how to avoid it.

***

Source Code Used in This Book

You can download all the source code and examples discussed within this book from the publisher's website.

© Copyright Pearson Education. All rights reserved.

Table of Contents

	Foreword	1
	Introduction	3
	This Book's Scope	3
	The Intended Audience	4
	This Book's Scope	5
	References and Suggested Reading	5
1	Introduction to Object-Oriented Concepts	7
	Procedural Versus O-O Programming	8
	What Makes O-O Different from Procedural Programming?	11
	Procedural Programming	11
	O-O Programming	12
	What Exactly Is an Object?	12
	Object Data	12
	Object Behaviors	13
	What Exactly Is a Class?	16
	Classes Are Object Templates	17
	Attributes	18
	Methods	19
	Messages	19
	Using UML to Model a Class Diagram	20
	Encapsulation	20
	Interfaces	21
	Implementations	21
	A Real-World Example of the Interface/Implementation Paradigm	21
	A Java Example of the Interface/Implementation Paradigm	22
	Inheritance	23
	Superclasses and Subclasses	24
	Abstraction	25
	Is-a Relationships	26
	Polymorphism	27
	Composition	30
	Has-a Relationships	31
	Conclusion	31
2	How to Think in Terms of Objects	33
	Knowing the Difference Between the Interface and the Implementation	34
	The Interface	36
	The Implementation	37
	An Interface/Implementation Example	37
	Using Abstract Thinking when Designing Interfaces	41
	Giving the User the Minimal Interface Possible	43
	Determining the Users	44
	Object Behavior	45
	Environmental Constraints	45
	Identifying the Public Interfaces	45
	Identifying the Implementation	46
	Conclusion	47
	References	47
3	Advanced Object-Oriented Concepts	49
	Constructors	50
	When Is a Constructor Called?	50
	What's Inside a Constructor?	51
	The Default Constructor	51
	Using Multiple Constructors	52
	The Design of Constructors	56
	Error Handling	56
	Ignoring the Problem	56
	Checking for Problems and Aborting the Application	57
	Checking for Problems and Attempting to Recover	57
	Throwing an Exception	57
	The Concept of Scope	60
	Local Attributes	60
	Object Attributes	61
	Class Attributes	64
	Operator Overloading	65
	Multiple Inheritance	66
	Object Operations	67
	Conclusion	68
	References	68
4	The Anatomy of a Class	69
	The Name of the Class	70
	Comments	72
	Attributes	73
	Constructors	74
	Accessors	76
	Public Interface Methods	78
	Private Implementation Methods	79
	Conclusion	79
	References	79
5	Class Design Guidelines	81
	Identifying the Public Interfaces	83
	Hiding the Implementation	84
	Designing Robust Constructors (and Perhaps Destructors)	84
	Designing Error Handling into a Class	85
	Documenting a Class and Using Comments	86
	Building Objects with the Intent to Cooperate	86
	Designing with Reuse in Mind	87
	Designing with Extensibility in Mind	87
	Making Names Descriptive	87
	Abstracting Out Non-portable Code	88
	Providing a Way to Copy and Compare Objects	89
	Keeping the Scope as Small as Possible	89
	A Class Should Be Responsible for Itself	90
	Serializing and Marshalling Objects	91
	Designing with Maintainability in Mind	92
	Using Object Persistence	92
	Using Iteration	93
	Testing the Interface	93
	Conclusion	95
	References	96
6	Designing with Objects: The Software Development Process	97
	Design Guidelines	98
	Doing the Proper Analysis	102
	Developing a Statement of Work	102
	Gathering the Requirements	102
	Developing a Prototype of the User Interface	103
	Identifying the Classes	103
	Determining the Responsibilities of Each Class	103
	Determining How the Classes Interact with Each Other	104
	Creating a Class Model to Describe the System	104
	A Blackjack Example	104
	Using CRC Cards	106
	Identifying the Blackjack Classes	107
	Identifying the Classes' Responsibilities	111
	UML Use Cases: Identifying the Collaborations	118
	First Pass at CRC Cards	122
	UML Class Diagrams: The Object Model	124
	Prototyping the User Interface	125
	Conclusion	126
	References	126
7	Mastering Inheritance and Composition	127
	Inheritance	129
	Generalization and Specialization	132
	It's All in the Design	133
	Composition	135
	Representing Composition with UML	136
	Why Encapsulation Is Fundamental to O-O	138
	How Inheritance Weakens Encapsulation	139
	A Detailed Example of Polymorphism	141
	An Object Should Be Responsible for Itself	142
	Conclusion	146
	References	146
8	Frameworks and Reuse: Designing with Interfaces and Abstract Classes	147
	To Reuse or Not to Reuse?	148
	What Is a Framework?	148
	What Is a Contract?	150
	Abstract Classes	151
	Interfaces	154
	Making a Contract	159
	System Plug-in-Points	161
	An E-Business Example	161
	An E-Business Problem	162
	The Non-Reuse Approach	163
	An E-Business Solution	165
	The UML Object Model	165
	Conclusion	171
	References	171
9	Building Objects	173
	Composition Relationships	175
	Building in Phases	176
	Types of Composition	178
	Aggregations	178
	Associations	180
	Using Associations and Aggregations Together	181
	Avoiding Dependencies	181
	Cardinality	183
	Optional Associations	186
	Tying It All Together: An Example	186
	Conclusion	188
	References	188
A	An Overview of UML Used in This Book	189
	What Is UML?	190
	The Structure of a Class Diagram	190
	Attributes and Methods	192
	Attributes	192
	Methods	193
	Access Designations	193
	Inheritance	194
	Interfaces	195
	Composition	197
	Aggregations	197
	Associations	198
	Cardinality	200
	Conclusion	202
	References	203
B	The Evolution of Object-Oriented Languages	205
	O-O Languages	206
	Simula	206
	Smalltalk	206
	C++	207
	Java	208
	Supporting Object-Oriented Features	208
	Why Do New Languages Keep Coming Along?	208
	What Makes a State-of-the-Art Language?	209
	Conclusion	211
	References	212
	Index	213

Preface

Introduction

This Book's Scope

As the title indicates, this book is about the object-oriented (OO) thought process. Obviously, choosing the theme and title of the book are important decisions; however, these decisions were not all that simple. Numerous books deal with various levels of object orientation. Several popular books deal with topics including OO analysis, OO design, OO programming, design patterns, OO data (XML), the Unified Modeling Language (UML), OO Internet development, various OO programming languages, and many other topics related to OO development.

However, while pouring over all of these books, many people forget that all of these topics are built on a single foundation: how you think in OO ways. It is unfortunate, but software professionals often dive into these books without taking the appropriate time and effort to really understand the concepts behind the content.

I contend that learning OO concepts is not accomplished by learning a specific development method or a set of tools. Doing things in an OO manner is, simply put, a way of thinking. This book is all about the OO thought process.

Separating the methods and tools from the OO thought process is not easy. Many people are introduced to OO concepts via one of these methods or tools. For example, years ago, most C programmers were first introduced to object orientation by migrating directly to C++—before they were even remotely exposed to OO concepts. Other software professionals were first introduced to object orientation by presentations that included object models using UML—again, before they were even exposed directly to OO concepts. It is not unusual to find that programming books and courses defer OO concepts until later in the learning process.

It is important to understand the significant difference between learning OO concepts and using the methods and tools that support the paradigm. This came into focus for me before I worked on the first edition of this book when I read articles such as Craig Larman's "What the UML Is—and Isn't," In this article he states,

Unfortunately, in the context of software engineering and the UML diagramming language, acquiring the skills to read and write UML notation seems to sometimes be equated with skill in object-oriented analysis and design. Of course, this is not so, and the latter is much more important than the former. Therefore, I recommend seeking education and educational materials in which intellectual skill in object-oriented analysis and design is paramount rather than UML notation or the use of a case tool.

Although learning a modeling language is an important step, it is much more important to learn OO skills first. Learning UML before OO concepts is similar to learning how to read an electrical diagram without first knowing anything about electricity.

The same problem occurs with programming languages. As stated earlier, many C programmers moved into the realm of object orientation by migrating to C++ before being directly exposed to OO concepts. This would always come out in an interview. Many times developers who claim to be C++ programmers are simply C programmers using C++ compilers. Even now, with languages such as C# .NET, VB .NET, and Java well established, a few key questions in a job interview can quickly uncover a lack of OO understanding.

Early versions of Visual Basic are not OO. C is not OO, and C++ was developed to be backward compatible with C. Because of this, it is quite possible to use a C++ compiler (writing only C syntax) while forsaking all of C++'s OO features. Even worse, a programmer can use just enough OO features to make a program incomprehensible to OO and non-OO programmers alike.

Thus, it is of vital importance that while you're on the road to OO development, you first learn the fundamental OO concepts. Resist the temptation to jump directly into a programming language (such as VB .NET, C++, C# .NET or Java) or a modeling language (such as UML), and take the time to learn the object-oriented thought process.

In my first class in Smalltalk in the late 1980s, the instructor told the class that the new OO paradigm was a totally new way of thinking (despite the fact that it has been around since the 60s). He went on to say that although all of us were most likely very good programmers, about 10%–20% of us would never really grasp the OO way of doing things. If this statement is indeed true, it is most likely because some people never really take the time to make the paradigm shift and learn the underlying OO concepts.

What's New in the Third Edition

As stated often in this introduction, my vision for the first edition was primarily a conceptual book. Although I still adhere to this goal for the second and third editions, I have included several application topics that fit well with object-oriented concepts. For the third edition I expand on many of the topics of the second edition and well as include totally new chapters. These revised and updated concepts

• XML is used for object communication.

• Object persistence and serialization.

• XML integrated into the languages object definition.

• Adding properties to attributes.

• XML-based Internet applications.

• Client/Server technologies.

• Expanded code examples in Java, C# .NET and VB .NET.

The chapters that cover these topics are still conceptual in nature; however, many of the chapters include Java code that shows how these concepts are implemented. In this third edition, a code appendix is included that presents the chapter's examples in C# .NET and Visual Basic .NET.

The Intended Audience

This book is a general introduction to fundamental OO concepts with code examples to reinforce the concepts. One of the most difficult juggling acts was to keep the material conceptual while still providing a solid, technical code base. The goal of this book is to allow a reader to understand the concepts and technology without having a compiler at hand. However, if you do have a compiler available, then there is code to be investigated.

The intended audience includes business managers, designers, developers, programmers, project managers, and anyone who wants to gain a general understanding of what object orientation is all about. Reading this book should provide a strong foundation for moving to other books covering more advanced OO topics.

Of these more advanced books, one of my favorites remains Object-Oriented Design in Java by Stephen Gilbert and Bill McCarty. I really like the approach of the book, and have used it as a textbook in classes I have taught on OO concepts. I cite Object-Oriented Design in Java often throughout this book, and I recommend that you graduate to it after you complete this one.

Other books that I have found very helpful include Effective C++ by Scott Meyers, Classical and Object-Oriented Software Engineering by Stephen R. Schach, Thinking in C++ by Bruce Eckel, UML Distilled by Martin Flower, and Java Design by Peter Coad and Mark Mayfield.

The conceptual nature of this book provides a unique perspective in regards to other computer technology books. While books that focus on specific technologies, such as programming languages, struggle with the pace of change, this book has the luxury of presenting established concepts that, while certainly being fine-tuned, do not experience radical changes. With this in mind, many of the books that were referenced several years ago, are still referenced because the concepts are still fundamentally the same.

This Book's Scope

It should be obvious by now that I am a firm believer in becoming comfortable with the object-oriented thought process before jumping into a programming language or modeling language. This book is filled with examples of code and UML diagrams; however, you do not need to know a specific programming language or UML to read it. After all I have said about learning the concepts first, why is there so much Java, C# .NET, and VB .NET code and so many UML diagrams? First, they are all great for illustrating OO concepts. Second, both are vital to the OO process and should be addressed at an introductory level. The key is not to focus on Java, C# .NET, and VB .NET or UML, but to use them as aids in the understanding of the underlying concepts.

The Java, C# .NET and VB .NET examples in the book illustrate concepts such as loops and functions. However, understanding the code itself is not a prerequisite for understanding the concepts; it might be helpful to have a book at hand that covers specific languages syntax if you want to get more detailed.

I cannot state too strongly that this book does not teach Java, C# .NET, and VB .NET or UML, all of which can command volumes unto themselves. It is my hope that this book will whet your appetite for other OO topics, such as OO analysis, object-oriented design, and OO programming.

This Book's Conventions

The following conventions are used in this book:

• Code lines, commands, statements, and any other code-related terms appear in a monospace typeface.

• Placeholders that stand for what you should actually type appear in italic monospace . Text that you should type appears in bold monospace .

• Throughout the book, there are special sidebar elements, such as

---

Note - A Note presents interesting information related to the discussion—a little more insight or a pointer to some new technique.

---

---

Tip - A Tip offers advice or shows you an easier way of doing something.

---

---

Caution - A Caution alerts you to a possible problem and gives you advice on how to avoid it.

---

Source Code Used in This Book

You can download all the source code and examples discussed within this book from the publisher's website.

© Copyright Pearson Education. All rights reserved.

Editorial Reviews

Introduces the fundamental object-oriented concepts to experienced programmers interested in learning object-oriented programming languages. Class design, inheritance, composition, interfaces, and abstract classes are covered. Annotation c. Book News, Inc., Portland, OR (booknews.com)

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