Design Patterns Tutorial (original) (raw)
Last Updated : 6 May, 2026
Design patterns are reusable solutions to common software design problems that help developers build cleaner and more maintainable systems. They act as templates for solving issues related to object creation, structure, and behavior. Instead of complete code, they provide blueprints that can be adapted to different scenarios.
- Provide standard terminology and best practices, making communication easier among developers.
- Help create structured, scalable, and maintainable code by promoting proven design approaches.
- Reduce development time by offering ready-made solutions to recurring problems.
Characteristics
These characteristics highlight how design patterns help in building efficient, scalable, and maintainable software systems.
- **Reusability: Patterns can be applied to different projects and problems, saving time and effort in solving similar issues.
- **Standardization: They provide a shared language and understanding among developers, helping in communication and collaboration.
- **Efficiency: By using these popular patterns, developers can avoid finding the solution to same recurring problems, which leads to faster development.
- **Flexibility: Patterns are abstract solutions/templates that can be adapted to fit various scenarios and requirements.
Design Pattern Basics
Design patterns provide reusable solutions to common software design problems. They help developers write cleaner, maintainable, and scalable applications.
Creational Design Patterns
Creational Design Patterns deal with object creation in a flexible and efficient manner. They help you control how and when objects are instantiated.
- Singleton Pattern
- Factory Method Pattern
- Abstract Factory Pattern
- Builder Pattern
- Prototype Pattern
- Object Pool Pattern
- Lazy Initialization
Structural Design Patterns
Structural patterns explain how classes and objects are combined to form larger structures. They improve code flexibility by simplifying relationships between components.
- Adapter Pattern
- Decorator Pattern
- Facade Pattern
- Composite Pattern
- Proxy Pattern
- Bridge Pattern
- Flyweight Pattern
Behavioral Design Patterns
Behavioral patterns define how objects communicate and distribute responsibilities. They help manage workflows, interactions, and decision-making within a system
- Observer Pattern
- Strategy Pattern
- Command Pattern
- Chain of Responsibility Pattern
- Template Method Pattern
- Iterator Pattern
- State Pattern
- Mediator Pattern
- Memento Pattern
- Visitor Pattern
Advanced Design Pattern
Advanced topics cover architectural principles and deeper system-design concepts. They help you build enterprise-level, scalable, and robust software systems
- SOLID Principles
- DRY Principle
- KISS Principle
- YAGNI Principle
- Dependency Injection Pattern
- Composition Vs Inheritance
- Event-Driven Architecture
- CQRS Design Pattern
- Event Sourcing Patterns
- CQRS Vs Event Sourcing Patterns
- Repository Pattern
- MVC Design Pattern
Design Pattern Interview Questions
This section prepares you for common interview questions on design patterns. It strengthens conceptual clarity and helps you explain patterns confidently.
Approach to Learn Design Patterns
- **Week 1: You'll learn the foundations needed for design patterns, including classes, objects, abstraction, inheritance, polymorphism, and encapsulation. You will also study SOLID principles, which help you write clean, maintainable, and loosely coupled code - essential before learning design patterns.
- **Week 2: Focuses on Creational Patterns such as Singleton, Factory Method, Abstract Factory, Builder, and Prototype. You'll understand how these patterns manage object creation, reduce code complexity, and improve flexibility.
- **Week 3: You’ll explore Adapter, Decorator, Facade, Composite, Proxy, Bridge, and Flyweight patterns. These patterns teach you how to structure classes and objects efficiently, simplifying complex systems.
- **Week 4: Dives into Strategy, Observer, Command, Chain of Responsibility, Iterator, Mediator, State, Template Method, and more. You’ll learn how objects communicate, coordinate actions, and share responsibilities in real systems.
- **Week 5: You'll study system-level patterns like MVC, MVVM, Dependency Injection, Repository Pattern, and Service Layer Pattern. These patterns are widely used in backend systems, frameworks, and enterprise applications.
- **Week 6: Helps you apply patterns to real situations: Logger (Singleton), Notification System (Observer), Payment Gateway (Strategy), Undo/Redo (Command), and API Facade (Facade Pattern). This week focuses fully on hands-on implementation.
- **Week 7: Covers low-level design problems where design patterns are essential. You’ll practice Parking Lot System, In-Memory File System, BookMyShow LLD, and securing Singleton from Reflection, Cloning, and Serialization.
- **Week 8: You'll build real-world projects using multiple design patterns combined. You’ll also revise interview questions, pattern comparisons, and architecture-based solutions to strengthen your problem-solving skills.