Table of Contents

• Chapter 1: Introduction to Java and Object-Oriented Programming 1
  • Why Java?1
  • What is Object-Oriented Programming?4
  • The Four Pillars of OOP8
  • Java Tools and Environment Setup14
  • Writing Your First Java Class16
Chapter 2: Classes and Objects 19
• Defining Classes and Creating Objects19
• Fields and Methods22
• The this Keyword28
• Constructors and Constructor Overloading30
• Object Lifecycle and Scope35
Chapter 3: Encapsulation 37
• Access Modifiers (private, public, protected, default)37
• Getters and Setters41
• Immutable Objects47
• JavaBeans and Encapsulation in Practice51
Chapter 4: Inheritance 54
• extends Keyword and Inheriting Methods54
• Method Overriding58
• super Keyword62
• Constructors and Inheritance67
• Inheritance Best Practices70
Chapter 5: Polymorphism 71
• Compile-time vs Runtime Polymorphism71
• Upcasting and Downcasting74
• Dynamic Method Dispatch78
• Practical Use Cases for Polymorphism81
Chapter 6: Abstraction 89
• Abstract Classes89
• Abstract Methods95
• Interfaces and implements100
• Differences Between Abstract Classes and Interfaces105
• Functional Interfaces (Intro)108
Chapter 7: Composition and Aggregation 110
• "Has-a" Relationships110
• Composition vs Inheritance115
• Designing for Reuse121
• Example: Modeling a Car with Components127
Chapter 8: Inner Classes and Anonymous Classes 134
• Member Classes134
• Static Nested Classes137
• Local Classes141
• Anonymous Classes and Functional Use Cases144
Chapter 9: Packages and Modular Design 147
• Organizing Code with Packages147
• Access Control Across Packages150
• Introduction to Java Modules (module-info.java)153
Chapter 10: Exception Handling and Design 156
• The Exception Hierarchy156
• Checked vs Unchecked Exceptions161
• Creating Custom Exceptions164
• Exception Handling as a Design Tool170
Chapter 11: SOLID Principles in Java 173
• Single Responsibility Principle173
• Open/Closed Principle178
• Liskov Substitution Principle182
• Interface Segregation Principle185
• Dependency Inversion Principle191
Chapter 12: DRY, KISS, YAGNI, and Other Principles 196
• Avoiding Code Duplication (DRY)196
• Keeping It Simple and Modular (KISS)199
• Avoiding Premature Optimization (YAGNI)202
Chapter 13: Design by Contract and Defensive Programming 204
• Preconditions, Postconditions, Invariants204
• Assertions208
• Defensive Copies211
Chapter 14: Object-Oriented Design Patterns (Essentials) 213
• What Are Design Patterns?213
• Creational Patterns: Singleton, Factory, Builder216
• Structural Patterns: Adapter, Decorator, Composite223
• Behavioral Patterns: Strategy, Observer, Command232
Chapter 15: Refactoring to Design 242
• Code Smells and Refactoring242
• Extract Method, Class, and Interface245
• Replace Conditional with Polymorphism250
• Applying Patterns Through Refactoring253
Chapter 16: Generics and Type Abstraction 257
• Generic Classes and Methods257
• Bounded Type Parameters262
• Wildcards (? extends, ? super)264
• Generics in Collections267
Chapter 17: Enums, Records, and Sealed Classes 271
• Using Enums in OOD271
• Java Records for Immutable Data Models275
• Sealed Classes and Controlled Inheritance278
Chapter 18: Lambda Expressions and Functional Interfaces 282
• What is Functional Programming in Java?282
• Lambdas in OOP Design285
• Function, Predicate, Consumer Interfaces288
• Stream API and Composition291
Chapter 19: Case Study 1 Designing a Library System 295
• Requirements Analysis295
• Domain Modeling298
• Code Implementation302
Chapter 20: Case Study 2 Online Shopping Cart System 314
• Managing Products and Inventory314
• User and Cart Design318
• Applying Patterns and Principles325
• Testing and Validation333
Chapter 21: Case Study 3 Task Manager App with JavaFX 336
• MVC in Object-Oriented GUI Design336
• Layered Architecture340
• Integrating User Interface and Business Logic345
Chapter 22: Unit Testing and Design with JUnit 351
• Writing Unit Tests for OOP Code351
• Test-Driven Development (TDD)355
• Mocking and Dependency Injection359
Chapter 23: Clean Code and Maintainable Design 364
• Naming, Formatting, and Readability364
• Reducing Coupling and Increasing Cohesion367
• Reusability and Extensibility370
Chapter 24: Designing for Change: Flexibility and Scalability 374
• Open-Ended Design with Interfaces374
• Strategy for Extensible Systems377
• Designing APIs380