Table of Contents
Introduction 1
1 Introduction to Object-Oriented Concepts 5
2 How to Think in Terms of Objects 37
3 Advanced Object-Oriented Concepts 53
4 The Anatomy of a Class 75
5 Class Design Guidelines 87
6 Designing with Objects 103
7 Mastering Inheritance and Composition 129
8 Frameworks and Reuse: Designing with Interfaces and Abstract Classes 151
9 Building Objects 179
10 Creating Object Models with UML 193
11 Objects and Portable Data: XML 207
12 Persistent Objects: Serialization and Relational Databases 225
13 Objects and the Internet 247
14 Objects and Client/Server Applications 271
15 Design Patterns 287
Index 309
Forewords & Introductions
IntroductionIntroduction
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.
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 BookYou can download all the source code and examples discussed within this book from the publisher's website.
© Copyright Pearson Education. All rights reserved.
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