Describe the Open/Closed Principle and how design patterns support it.
OCP states that software entities (classes, modules, functions) should be open for extension but closed for modification. Design patterns like the Strategy and Decorator patterns allow for adding new functionality without changing existing code, adhering to OCP.
Top Design Patterns Interview Questions
A design pattern is basically a reusable and generalized solution to a common problem that arises during software design and development. Design patterns are not specific to a particular programming language or technology instead, they provide abstract templates or blueprints for solving recurring design-related problems. They help software developers create well-structured, maintainable, and flexible code by promoting best practices and proven solutions.
Top Interview Questions for Design Patterns
- 1. What is a Design Pattern?
- 2. What are the types of Design Patterns?
- 3. What are the advantages of using Design Patterns?
- 4. What are the types of creational Patterns?
- 5. What are the types of Structural patterns?
- 6. What are the types of Behavioral patterns?
- 7. What is Known as Gang of Four?
- 8. What is the Singleton pattern, and when would you use it?
- 9. Explain the Factory Method pattern and provide an example of its use.
- 10. Describe the Adapter pattern and provide an example of where it can be applied.
- 11. Provide a scenario where the Command pattern would be preferable to the Strategy pattern.
- 12. Explain the Single Responsibility Principle and its significance in software design.
- 13. What is the Observer pattern, and how does it enable objects to notify others of changes in state?
- 14. Describe the Open/Closed Principle and how design patterns support it.
- 15. How is the Bridge pattern different from the Adapter pattern?
- 16. How does the Dependency Inversion Principle promote loose coupling, and how is it related to design patterns?
- 17. Provide a real-world example of the Singleton pattern being used in a popular library or framework.
- 18. Provide an example where the Strategy pattern is used to switch between different algorithms.
- 19. When should you avoid using design patterns, and what are the potential drawbacks?
- 20. How can you ensure that design patterns do not lead to over-engineering or unnecessary complexity?
- 21. Provide a scenario where the Decorator pattern is used to enhance the functionality of an existing class in a codebase.
- 22. How can the Command pattern be applied in a user interface (UI) framework?
- 23. What is the role of a UML diagram in illustrating design patterns?
- 24. How can design patterns help with refactoring existing code?
- 25. Provide an example where the Strategy pattern is used to switch between different algorithms.