Designing with Objects Object-Oriented Design Patterns Explained with Stories from Harry Potter

by Kak, Avinash C.

• ISBN13: 9781118581209
• ISBN10: 1118581202
• eBook ISBN(s): 9781118902561
• Edition: 1st
• Format: Paperback
• Copyright: 2015-02-09
• Publisher: Wiley
• More Book Details

Summary

Here is a book that takes the sting out of learning object-oriented design patterns! Using vignettes from the fictional world of Harry Potter, author Avinash C. Kak provides a refreshing alternative to the typically abstract and dry object-oriented design literature.

Designing with Objects is unique. It explains design patterns using the short-story medium instead of sterile examples. It is the third volume in a trilogy by Avinash C. Kak, following Programming with Objects (Wiley, 2003) and Scripting with Objects (Wiley, 2008). Designing with Objects confronts how difficult it is for students to learn complex patterns based on conventional scenarios that they may not be able to relate to. In contrast, it shows that stories from the fictional world of Harry Potter provide highly relatable and engaging models. After explaining core notions in a pattern and its typical use in real-world applications, each chapter shows how a pattern can be mapped to a Harry Potter story. The next step is an explanation of the pattern through its Java implementation. The following patterns appear in three sections: Abstract Factory, Builder, Factory Method, Prototype, and Singleton; Adapter, Bridge, Composite, Decorator, Facade, Flyweight, and Proxy; and the Chain of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, and Visitor. For readers’ use, Java code for each pattern is included in the book’s companion website.

• All code examples in the book are available for download on a companion website with resources for readers and instructors.
• A refreshing alternative to the abstract and dry explanations of the object-oriented design patterns in much of the existing literature on the subject.
• In 24 chapters, Designing with Objects explains well-known design patterns by relating them to stories from the fictional Harry Potter series

Author Biography

Avinash C. Kak is Professor of Electrical and Computer Engineering at Purdue University. His areas of interest include software engineering, computer and network security, sensor networks, and computer vision (especially with camera networks). Professor Kak has been awarded numerous Best Teacher of the Year awards at Purdue University. He is the author of Scripting with Objects and Programming with Objects, both published by Wiley.

Table of Contents

PREFACE xiv

ACKNOWLEDGMENTS xix

1 Why Learn Design Patterns and Why Do So with Help from Harry Potter? 1

1.1 The OO Design Patterns “Bible” by GoF 2

1.2 But What Has Harry Potter Got to Do with OO Design Patterns? 4

1.3 Is Familiarity with Harry Potter a Requirement for Understanding This Book? 6

1.4 How the Pattern Explanations are Organized 7

1.5 The Terminology of Object-Oriented Programming 7

1.6 The UML Notation Used in the Class Diagrams 12

1.6.1 Association as a Relationship Between Classes 14

1.6.2 Aggregation and Composition as Relationships Between Classes 15

1.6.3 Representing Attributes 16

1.6.4 Representing Operations 17

I CREATIONAL PATTERNS 19

2 Abstract Factory 21

2.1 The Concept of a Factory in Software 21

2.2 Intent and Applicability 22

2.3 Introduction to the Abstract Factory Pattern 22

2.4 The Abstract Factory Pattern in Real-World Applications 23

2.5 Harry Potter Story Used to Illustrate the Abstract Factory Pattern 23

2.6 A Top Level View of the Pattern Demonstration 25

2.7 The Abstract Class Factory 27

2.8 The Helper Class FactoryStore 27

2.9 The Abstract Class Enchanted 30

2.10 The Concrete Classes for Magical Objects 31

2.11 The Concrete Factory Classes 32

2.12 The Client Class Diagon AlleyRetailer 34

2.13 Playing with the Code 36

3 Builder 38

3.1 Building Complex Objects 38

3.2 Intent and Applicability 39

3.3 Introduction to the Builder Pattern 39

3.4 The Builder Pattern in Real-World Applications 41

3.5 Harry Potter Story Used to Illustrate the Builder Pattern 42

3.6 A Top-Level View of the Pattern Demonstration 43

3.7 The Abstract Class PotionMaker 45

3.8 The Concrete Extensions of PotionMaker 46

3.9 The Director Class 52

3.10 The Potion Class 54

3.11 The Ingredient Class 55

3.12 The PotionMakingFeasibilityViolation Class 55

3.13 The Client Class 55

3.14 Playing with the Code 56

4 Factory Method 59

4.1 Revisiting the Concept of a Factory in Software 59

4.2 Intent and Applicability 60

4.3 Introduction to the Factory Method Pattern 60

4.4 The Factory Method Pattern in Real-World Applications 61

4.5 Harry Potter Story Used to Illustrate the Factory Method Pattern 62

4.6 A Top Level View of the Pattern Demonstration 63

4.7 The Enchanted Class Hierarchy 65

4.8 The ArtifactFactory Class Hierarchy and the Factory Methods Contained Therein 68

4.9 The Client Class 70

4.10 Playing with the Code 71

5 Prototype 73

5.1 Why Not Make New Objects by Copying Old Objects? 73

5.2 Intent and Applicability 74

5.3 Introduction to the Prototype Pattern 74

5.4 The Prototype Pattern in Real-World Applications 77

5.5 Harry Potter Story Used to Illustrate The Prototype Pattern 78

5.6 A Top Level View of the Pattern Demonstration 79

5.7 The Dragon Class 81

5.8 The PrototypeManagerAndDuplicator Class 84

5.9 The DragonAficionado Class 87

5.10 The UnknownDragonException Class 88

5.11 Playing with the Code 88

6 Singleton 90

6.1 Singular Objects 90

6.2 Intent and Applicability 90

6.3 Introduction to the Singleton Pattern 91

6.4 The Singleton Pattern in Real-World Applications 91

6.5 Harry Potter Story Used to Illustrate the Singleton Pattern 92

6.6 A Top Level View of the Pattern Demonstration 92

6.7 The MinisterForMagic Class 93

6.8 The TestSingleton Class 94

6.9 Variations on the Singleton Pattern 95

6.10 Playing with the Code 97

II STRUCTURAL PATTERNS 99

7 Adapter 101

7.1 Getting Things to Work Together 101

7.2 Intent and Applicability 102

7.3 Introduction to the Adapter Pattern 102

7.4 The Adapter Pattern in Real-World Applications 103

7.5 Harry Potter Story Used to Illustrate the Adapter Pattern 104

7.6 A Top Level View of the Pattern Demonstration 104

7.7 The Target Interface: TeachingDADA 106

7.8 The TeacherForDADA Class 107

7.9 The AdapterForSafeTeaching Class 108

7.10 The Client Class SchoolOfMagic 110

7.11 Object Adapter 111

7.12 Pluggable Adapter 113

7.13 Playing with the Code 119

8 Bridge 122

8.1 Concepts and Their Implementation 122

8.2 Intent and Applicability 123

8.3 Introduction to the Bridge Pattern 123

8.4 The Bridge Pattern in Real-World Applications 126

8.5 Harry Potter Story Used to Illustrate the Bridge Pattern 127

8.6 A Top Level View of the Pattern Demonstration 130

8.7 The Humanoid Class 130

8.8 The Dementor, Goblin, and HouseElf Classes 132

8.9 The Humanoid Imp Class 134

8.10 Implementation Classes for the Dementor, Goblin, and HouseElf Classes 137

8.11 The Client Class MinistryOfMagic 139

8.12 Playing with the Code 140

9 Composite 142

9.1 Relationships That Loop Back 142

9.2 Intent and Applicability 143

9.3 Introduction to the Composite Pattern 144

9.4 The Composite Pattern in Real-World Applications 145

9.5 Harry Potter Story Used to Illustrate the Composite Pattern 146

9.6 A Top Level View of the Pattern Demonstration 147

9.7 The WizardTraits Interface 148

9.8 The Wizard Class 149

9.9 The Auror Class 152

9.10 The Obliviator Class 153

9.11 The DepartmentHead Class 155

9.12 The Minister for Magic Class 156

9.13 The Client Class Test 158

9.14 Playing with the Code 159

10 Decorator 161

10.1 Onion as a Metaphor 161

10.2 Intent and Applicability 162

10.3 Introduction to the Decorator Pattern 162

10.4 The Decorator Pattern in Real-World Applications 164

10.5 Harry Potter Story Used to Illustrate the Decorator Pattern 165

10.6 A Top Level View of the Pattern Demonstration 168

10.7 The CoreMessageDeliveryClass Class 170

10.8 The Decorator Classes 170

10.9 The Client Class Test 172

10.10 Playing with the Code 173

11 Facade 175

11.1 Hiding Complexity 175

11.2 Intent and Applicability 175

11.3 Introduction to the Facade Pattern 176

11.4 The Facade Pattern in Real-World Applications 177

11.5 Harry Potter Story Used to Illustrate the Facade Pattern 177

11.6 A Top Level View of the Pattern Demonstration 179

11.7 The Abstract Root Class Facade 181

11.8 The Network Class 183

11.9 The Node, Link, and Path Classes 193

11.10 The Three Concrete Facade Classes 198

11.11 Testing the Demonstration Code 203

11.12 Playing with the Code 207

12 Flyweight 212

12.1 The Idea of Customized Duplications 212

12.2 Intent and Applicability 213

12.3 Introduction to the Flyweight Pattern 213

12.4 The Flyweight Pattern in Real-World Applications 214

12.5 Harry Potter Story Used to Illustrate the Flyweight Pattern 214

12.6 A Top Level View of the Pattern Demonstration 215

12.7 The HeadMasterPortrait Class 218

12.8 The FlyweightImageStore Class 218

12.9 The ImageManager Class 219

12.10 The PortraitBorderChoices Class 225

12.11 The ImageNotAvailableException Class 226

12.12 The PortraitMakerAssignment Class 226

12.13 Playing with the Code 228

12.14 Acknowledgment 229

13 Proxy 230

13.1 Is It Always Necessary to Have the Real Thing? 230

13.2 Intent and Applicability 230

13.3 Introduction to the Proxy Pattern 231

13.4 The Proxy Pattern in Real-World Applications 232

13.5 Harry Potter Story Used to Illustrate the Proxy Pattern 233

13.6 A Top Level View of the Pattern Demonstration 235

13.7 The Abstract Class Wizard 235

13.8 The DarkWizardTraits Interface 237

13.9 The DarkWizard Class 238

13.10 The DarkLord Class 242

13.11 The ClientClass Class 245

13.12 Playing with the Code 246

III BEHAVIORAL PATTERNS 249

14 Chain of Responsibility 253

14.1 Passing the Buck 253

14.2 Intent and Applicability 254

14.3 Introduction to the Chain of Responsibility Pattern 254

14.4 The Chain of Responsibility Pattern in Real-World Applications 255

14.5 Harry Potter Story Used to Illustrate the Chain of Responsibility Pattern 256

14.6 A Top Level View of the Pattern Demonstration 258

14.7 The Interface Class Violations 260

14.8 The Abstract Class Adjudicator 261

14.9 The Player Class 263

14.10 The Classes with the Authority to Resolve Violations 265

14.11 Testing the Code 268

14.12 Playing with the Code 269

15 Command 272

15.1 Actions Versus the Actors 272

15.2 Intent and Applicability 273

15.3 Introduction to the Command Pattern 274

15.4 The Command Pattern in Real-World Applications 274

15.5 Harry Potter Story Used to Illustrate the Command Pattern 276

15.6 A Top Level View of the Pattern Demonstration 277

15.7 The Command Interface 279

15.8 The MyPlaces Interface 279

15.9 The ProtectHarryPotter Class 279

15.10 The Wizard Class 282

15.11 The Squib Class 284

15.12 The Invoker Class 285

15.13 The UnableToProtectHarryPotterException Class 286

15.14 The Client Class 286

15.15 Playing with the Code 288

16 Interpreter 290

16.1 Parsing versus Interpretation 290

16.2 Intent and Applicability 292

16.3 Introduction to the Interpreter Pattern 292

16.4 The Interpreter Pattern in Real-World Applications 293

16.5 Harry Potter Story Used to Illustrate the Interpreter Pattern 294

16.6 A Parser Front-End for the Interpreter Pattern 296

16.7 A Top Level View of the Pattern Demonstration 304

16.8 The Driver Class 307

16.9 The Interpreter Sentence Class 310

16.10 The Worker Classes for Interpretation 312

16.11 The Utility Class ShowSyntaxTree 315

16.12 Playing with the Code 316

17 Iterator 321

17.1 Storing Object Collections and Interacting with Them 321

17.2 Intent and Applicability 323

17.3 Introduction to the Iterator Pattern 323

17.4 The Iterator Pattern in Real-World Applications 324

17.5 Harry Potter Story Used to Illustrate the Iterator Pattern 325

17.6 A Top Level View of the Pattern Demonstration 326

17.7 A Utility Interface for Demonstrating the Iterator Pattern 328

17.8 The Iterator Interface 330

17.9 The Fresher Class 330

17.10 The SortingHat Class 334

17.11 The MagicCollection Interface 344

17.12 The MagicList and MagicSet Classes 344

17.13 The Class Range 349

17.14 Playing with the Code 349

17.15 Credits 352

18 Mediator 353

18.1 The Role of Mediation in Collaborative Problem Solving 353

18.2 Intent and Applicability 354

18.3 Introduction to the Mediator Pattern 354

18.4 The Mediator Pattern in Real-World Applications 355

18.5 Harry Potter Story Used to Illustrate the Mediator Pattern 357

18.6 A Top Level View of the Pattern Demonstration 357

18.7 The Abstract Class Mediator 359

18.8 The Interface TrialElements 360

18.9 The MinistryOfMagicTrialMediator Class 361

18.10 The Witness Class 366

18.11 The Trial Interface 367

18.12 The HarryPotterTrial Class 367

18.13 Playing with the Code 369

19 Memento 371

19.1 Recalling the Past 371

19.2 Intent and Applicability 372

19.3 Introduction to the Memento Pattern 372

19.4 The Memento Pattern in Real-World Applications 374

19.5 Harry Potter Story Used to Illustrate the Memento Pattern 374

19.6 A Top Level View of the Pattern Demonstration 377

19.7 The HogwartsHappening Class and The Inner Memento Class 378

19.8 The Client Class 380

19.9 Playing with the Code 384

20 Observer 386

20.1 Subscription-Based Broadcasting 386

20.2 Intent and Applicability 387

20.3 Introduction to the Observer Pattern 387

20.4 The Observer Pattern in Real-World Applications 388

20.5 Harry Potter Story Used to Illustrate the Observer Pattern 389

20.6 A Top Level View of the Pattern Demonstration 391

20.7 The Observer Interface 391

20.8 The Observable Interface 393

20.9 The DarkLord Class 393

20.10 The DeathEater Class 396

20.11 The GodProcess Class 399

20.12 Playing with the Code 401

21 State 405

21.1 Contextual Dependence of Behaviors 405

21.2 Intent and Applicability 406

21.3 Introduction to the State Pattern 406

21.4 The State Pattern in Real-World Applications 406

21.5 Harry Potter Story Used to Illustrate the State Pattern 407

21.6 A Top Level View of the Pattern Demonstration 408

21.7 The DADA State Interface 410

21.8 The Year-by-Year Implementation Classes for the State 411

21.9 The TeachingDADA Class 417

21.10 The Hogwarts Class 418

21.11 Playing with the Code 419

22 Strategy 421

22.1 Strategies in the Pursuit of Goals 421

22.2 Intent and Applicability 422

22.3 Introduction to the Strategy Pattern 422

22.4 The Strategy Pattern in Real-World Applications 423

22.5 Harry Potter Story Used to Illustrate the Strategy Pattern 424

22.6 A Top Level View of the Pattern Demonstration 425

22.7 The Abstract Root Class for Strategies: StrategyAbstractRoot 428

22.8 The Concrete Strategy Classes 429

22.9 The Champion Class 432

22.10 The SecondTaskManager Class 434

22.11 Playing with the Code 436

23 Template Method 437

23.1 Customizable Recipes 437

23.2 Intent and Applicability 438

23.3 Introduction to the Template Method Pattern 438

23.4 The Template Method Pattern in Real-World Applications 440

23.5 Harry Potter Story Used to Illustrate the Template Method Pattern 441

23.6 A Top Level View of the Pattern Demonstration 442

23.7 The Abstract Root of Narrative Generation Classes 444

23.8 Concrete Classes for Narrative Generation 445

23.9 The Executable Class 449

23.10 Playing with the Code 450

24 Visitor 453

24.1 Hooks, Good and Evil 453

24.2 Intent and Applicability 454

24.3 Introduction to the Visitor Pattern 454

24.4 The Visitor Pattern in Real-World Applications 457

24.5 Harry Potter Story Used to Illustrate the Visitor Pattern 457

24.6 A Top Level View of the Pattern Demonstration 459

24.7 The Visitor Interface 460

24.8 Two Concrete Implementations of the Visitor Interface 462

24.9 A Re-Implementation of the Wizard Hierarchy of the Composite Pattern 463

24.10 The Executable Class Client 469

24.11 Playing with the Code 470

REFERENCES 473

INDEX 474