A simple Java console application simulating a basic library system, built to practice object-oriented programming concepts from:
"The Object-Oriented Thought Process" – Matt Weisfeld
- Encapsulation
- Abstraction & Inheritance
- Polymorphism
- Composition over Inheritance
- Interfaces
- Dependency Injection
- SOLID Principles
| Principle | Applied | Explanation |
|---|---|---|
| S – Single Responsibility | ✅ | Each class has one job: loaning, user handling, notification, etc. |
| O – Open/Closed | ✅ | New book types (e.g., Article, Novel) can be added without changing existing logic. |
| L – Liskov Substitution | ✅ | Book references accept any subclass without breaking behavior. |
| I – Interface Segregation | Not critical yet; single interface is enough for now. | |
| D – Dependency Inversion | ✅ | LoanManager depends on NotificationService interface, not a concrete class. |
Book,User,LoanRecord– domain entitiesLoanManager,BookManager,UserManager– business logicNotificationService,EmailNotificationService– interface & implementationLibrary– orchestrator classLoanManagerTest– unit tests using JUnit 5 & Mockito
- Java 21
- Maven
- JUnit 5
- Mockito
mvn clean test