Object-Oriented Programming (Java) Q&A (75 Questions) | UML, Design Patterns, OOP Principles | Software Engineering

This document features 75 exam-style questions and verified answers focused on Object-Oriented Programming (OOP) using Java, curated for the 2025/2026 academic year. It serves as a high-quality academic resource for students preparing for OOP-related exams, certifications, or interviews in both theoretical and practical contexts. The content covers the fundamental OOP pillars: Encapsulation, Inheritance, and Polymorphism, while also diving deeper into critical principles like cohesion vs coupling, roles and responsibilities, and object relationships such as is-a, has-a, and uses-a. It explores advanced topics like upcasting and downcasting, static members, and the Liskov Substitution Principle. In addition, the document includes a strong focus on UML (Unified Modeling Language), detailing diagrams such as: Use Case Diagrams (actors, extends, includes) Class Diagrams (aggregation, composition, dependency, multiplicity) Sequence Diagrams (object interaction and message flow) Students will also benefit from concise definitions and usage explanations of key design patterns, such as: Singleton Pattern Iterator Pattern Adapter Pattern Facade Pattern Moreover, the material touches on Object-Oriented Analysis (OOA) and Object-Oriented Design (OOD) processes, software design principles, Agile methodology, and best practices like the Law of Demeter. This document is highly valuable for: Students of Software Engineering, Computer Science, Information Technology, and Systems Analysis Candidates preparing for Java OOP exams or object modeling interviews Instructors and tutors seeking clear, structured review content Developers seeking a concise reference for UML and OOP best practices Keywords: Object-Oriented Programming, Java, encapsulation, inheritance, polymorphism, UML diagrams, use case diagram, class diagram, sequence diagram, aggregation, composition, design patterns, singleton pattern, iterator pattern, adapter pattern, facade pattern, static members, Liskov principle, object-oriented design, object-oriented analysis, cohesion, coupling, software components, Java interfaces, upcasting, downcasting, agile software development