Q: What are design patterns?
A: Design patterns are general reusable solutions to common problems that occur in software design. They provide proven solutions to common software design challenges and can improve the quality and maintainability of software.
Q: What are the types of design patterns?
A: There are three main types of design patterns: creational patterns, structural patterns, and behavioral patterns.
Q: What is the Singleton design pattern?
A: The Singleton pattern is a creational pattern that ensures that only one instance of a class is created and provides a global point of access to that instance. This pattern is often used for resources that are expensive to create or need to be shared across the application.
Q: What is the Factory design pattern?
A: The Factory pattern is a creational pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created. This pattern is often used when you don't know the exact types of objects you need to create until runtime.
Q: What is the Observer design pattern?
A: The Observer pattern is a behavioral pattern that defines a one-to-many dependency between objects, so that when one object changes state, all its dependents are notified and updated automatically. This pattern is often used in event-driven architectures, where one component needs to notify other components of its state changes.
Q: What is the Strategy design pattern?
A: The Strategy pattern is a behavioral pattern that allows you to define a family of algorithms, encapsulate each one, and make them interchangeable at runtime. This pattern is often used when you need to change the behavior of an object dynamically, depending on the context or user input.
Q: What is the Decorator design pattern?
A: The Decorator pattern is a structural pattern that allows you to add functionality to an object dynamically, without changing its core functionality. This pattern is often used when you need to add features or functionality to an object at runtime, without modifying its source code.
Q: What is the MVC design pattern?
A: The Model-View-Controller (MVC) pattern is a design pattern that separates the presentation layer (the view) from the data and logic layers (the model and controller). This pattern is often used in web development and GUI applications to improve separation of concerns and maintainability.
Q: What is the Dependency Injection design pattern?
A: The Dependency Injection (DI) pattern is a design pattern that separates the creation of objects and their dependencies from their usage, and provides these dependencies to the object at runtime. This pattern is often used to reduce coupling between objects, improve testability, and increase flexibility and maintainability of the application.
These are just a few commonly asked design patterns interview questions and answers. Be sure to study and practice before your interview, and be prepared to discuss your experience and knowledge of design patterns in depth.