Object-Oriented Programming
Encapsulation & Access Control
Bank Account with Private State
User Factory - Static Factory Method Pattern
Inheritance & Polymorphism
Polymorphic Shape Area Calculator
Vehicle Registry with Polymorphic Speed
Operation Enum with Behavior
Polymorphic Retail Product Catalog
Multi-Format Media Metadata Extractor
Smart Home Device Controller
Payment Processor with Pluggable Providers
Plugin-Based Notification Dispatcher
Custom Exception Hierarchy with Global Handler
Smart Home Device Refactor
Logger Mixin Across Unrelated Classes
Payment Gateway Exception Handler
Value Objects & Immutability
Complex Number with Operator Overloading
Immutable Money Value Object
Point Equals and HashCode
Employee Comparable and Comparators
Immutable Point with Copy-on-Write API
Deep Copy Company Hierarchy
Generic Bounded Comparable Box