System Design
Dependency Inversion Principle in Java: Depend on Abstractions, Not Concrete Classes
Jason Yang · 12 May, 2026
Dependency Inversion Principle in Java, explained with notification, payment gateway, Spring Boot, and testing examples.
Blog posts — page 21
System Design
Interface Segregation Principle in Java: Many Small Interfaces Over One Large Interface
Jason Yang · 12 May, 2026
The Interface Segregation Principle in Java: why one fat interface forces empty methods and UnsupportedOperationException, and how small focused interfaces fix it — with phone, printer, and backend examples.
System Design
Liskov Substitution Principle in Java: Subclasses Should Replace Parent Classes Safely
Jason Yang · 12 May, 2026
The Liskov Substitution Principle in Java: why a subclass that breaks its parent's contract violates LSP, shown with bird, Flyable, and discount policy examples.
System Design
Open-Closed Principle in Java: Open to Extension, Closed to Modification
Jason Yang · 12 May, 2026
The Open-Closed Principle in Java: add new behavior without touching stable code, shown with payment methods, interfaces, and Spring Boot style examples.
System Design
Single Responsibility Principle in Java: One Class, One Reason to Change
Jason Yang · 12 May, 2026
The Single Responsibility Principle in Java: what 'one reason to change' actually means in practice, with backend service and Spring Boot style examples.