Design Patterns Series: Creational Patterns & Singleton

𝗗𝗮𝘆 𝟭𝟯/𝟵𝟬: 𝗔𝗿𝗰𝗵𝗶𝘁𝗲𝗰𝘁𝘂𝗿𝗲 𝟭𝟬𝟭 — 𝗜𝗻𝘁𝗿𝗼 𝘁𝗼 𝗗𝗲𝘀𝗶𝗴𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀 Today a I took a step back from syntax to look at the "Big Picture": 𝗗𝗲𝘀𝗶𝗴𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀. 𝗪𝗵𝗮𝘁 𝗮𝗿𝗲 𝘁𝗵𝗲𝘆? In software engineering, a Design Pattern is a proven, reusable solution to a commonly recurring problem. Think of them as 𝗯𝗹𝘂𝗲𝗽𝗿𝗶𝗻𝘁𝘀 for solving specific architectural challenges. Instead of reinventing the wheel, we use these established industry standards to write cleaner, more efficient code. 𝗧𝗵𝗲 𝟯 𝗣𝗶𝗹𝗹𝗮𝗿𝘀 𝗼𝗳 𝗗𝗲𝘀𝗶𝗴𝗻 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀 I’m diving into the three main categories that every Full Stack developer should know: 1️⃣ 𝗖𝗿𝗲𝗮𝘁𝗶𝗼𝗻𝗮𝗹 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀:   • These focus on Object Creation logic.   • They help decide how an object is created to avoid unnecessary      complexity (e.g., controlling how many instances exist).  • 𝗘𝘅𝗮𝗺𝗽𝗹𝗲𝘀: Singleton, Factory, Builder. 2️⃣ 𝗦𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗮𝗹 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀:   • These focus on Class & Object Composition.   • They help different parts of a system work together smoothly.  • 𝗘𝘅𝗮𝗺𝗽𝗹𝗲𝘀: Adapter, Decorator, Proxy. 3️⃣ 𝗕𝗲𝗵𝗮𝘃𝗶𝗼𝗿𝗮𝗹 𝗣𝗮𝘁𝘁𝗲𝗿𝗻𝘀:   • These focus on Communication between objects.   • They define how objects interact and share responsibilities.  • 𝗘𝘅𝗮𝗺𝗽𝗹𝗲𝘀: Observer, Strategy, Command. My next post will be a detailed breakdown of the most famous (and sometimes controversial) pattern: The Singleton Design Pattern.  Coding is about solving problems, but Engineering is about solving them sustainably.  Design patterns are the secret to building applications that last. 👨💻🔥 #90DaysOfCode #DesignPatterns #SoftwareArchitecture #Java #PentagonSpace #FullStackDeveloper #CreationalPatterns #CleanCode #SoftwareEngineering

🚀 What is SOLID in Object-Oriented Design? If you're serious about writing maintainable, scalable, and testable code, you cannot ignore SOLID principles. SOLID is an acronym representing five foundational design principles in OOP: 🟢 S — Single Responsibility Principle (SRP) A class should have only one reason to change. ➡ Keep business logic, reporting, persistence, and validation separated. This reduces coupling and improves maintainability. 🟢 O — Open/Closed Principle (OCP) Software entities should be open for extension, closed for modification. ➡ Use abstractions and polymorphism to extend behavior without altering existing code. Prevents regression bugs and protects stable modules. 🟢 L — Liskov Substitution Principle (LSP) Derived classes must be substitutable for their base classes. ➡ Child classes should honor the behavioral contract of the parent. If replacing a superclass with a subclass breaks logic — LSP is violated. 🟢 I — Interface Segregation Principle (ISP) Clients should not depend on interfaces they don’t use. ➡ Prefer smaller, role-based interfaces over large “fat” interfaces. Improves flexibility and reduces unnecessary implementation. 🟢 D — Dependency Inversion Principle (DIP) High-level modules should depend on abstractions, not concrete implementations. ➡ Use interfaces and dependency injection. This is the backbone of frameworks like Spring. 💡 Why SOLID Matters? ✔ Cleaner architecture ✔ Easier unit testing ✔ Reduced technical debt ✔ Better scalability ✔ More readable and modular code In enterprise applications (especially in Spring Boot ecosystems), applying SOLID properly separates domain logic, services, repositories, and infrastructure layers effectively. If you’re building production-grade systems, SOLID isn’t optional — it’s foundational. #SoftwareEngineering #Java #SpringBoot #CleanCode #SystemDesign #OOP #SOLID

🚀 What is SOLID in Object-Oriented Design? If you're serious about writing maintainable, scalable, and testable code, you cannot ignore SOLID principles. SOLID is an acronym representing five foundational design principles in OOP: 🟢 S — Single Responsibility Principle (SRP) A class should have only one reason to change. ➡ Keep business logic, reporting, persistence, and validation separated. This reduces coupling and improves maintainability. 🟢 O — Open/Closed Principle (OCP) Software entities should be open for extension, closed for modification. ➡ Use abstractions and polymorphism to extend behavior without altering existing code. Prevents regression bugs and protects stable modules. 🟢 L — Liskov Substitution Principle (LSP) Derived classes must be substitutable for their base classes. ➡ Child classes should honor the behavioral contract of the parent. If replacing a superclass with a subclass breaks logic — LSP is violated. 🟢 I — Interface Segregation Principle (ISP) Clients should not depend on interfaces they don’t use. ➡ Prefer smaller, role-based interfaces over large “fat” interfaces. Improves flexibility and reduces unnecessary implementation. 🟢 D — Dependency Inversion Principle (DIP) High-level modules should depend on abstractions, not concrete implementations. ➡ Use interfaces and dependency injection. This is the backbone of frameworks like Spring. 💡 Why SOLID Matters? ✔ Cleaner architecture ✔ Easier unit testing ✔ Reduced technical debt ✔ Better scalability ✔ More readable and modular code In enterprise applications (especially in Spring Boot ecosystems), applying SOLID properly separates domain logic, services, repositories, and infrastructure layers effectively. If you’re building production-grade systems, SOLID isn’t optional — it’s foundational. #SoftwareEngineering #Java #SpringBoot #CleanCode #SystemDesign #OOP #SOLID

Most developers use design patterns. Few know when not to use them. Early in my career, I was obsessed with patterns: Factory, Strategy, Singleton… everywhere. Every problem looked like a chance to “apply a pattern.” Until one day, a simple service turned into: • 6 classes • 3 interfaces • Endless abstraction For a problem that needed… 50 lines of code. ⸻ That’s when it clicked: 👉 Design patterns are tools, not goals. ⸻ Take the Strategy Pattern: Great when: • You have multiple interchangeable behaviors • Logic changes frequently Overkill when: • You have 2 simple conditions • Logic is unlikely to evolve ⸻ What I follow now: • Start simple • Refactor when complexity actually appears • Introduce patterns only when they remove pain ⸻ Big lesson: Bad code ignores patterns. Overengineered code worships them. Good code uses them when needed. ⸻ Before using any pattern, ask: “Am I solving a real problem… or just showing I know this pattern?” ⸻ #DesignPatterns #Java #SoftwareEngineering #CleanCode #BackendDevelopment #SystemDesign

Creational Design Patterns — Three Patterns Every Developer Should Understand In software development, every system relies on objects. However, the way objects are created can significantly impact code flexibility, maintainability, and testability. Creational design patterns address this by providing structured approaches to object instantiation while reducing tight coupling between classes. Here are three essential creational patterns that are widely used in modern software development: 🔒 Singleton Pattern The Singleton pattern ensures that only one instance of a class exists within the application lifecycle and provides a global access point to it. This pattern is commonly used for shared resources such as configuration managers, logging services, and database connection pools where multiple instances could lead to inconsistencies or unnecessary resource usage. 🏭 Factory Method Pattern The Factory Method pattern delegates the responsibility of object creation to a dedicated factory component instead of instantiating objects directly within the code. This approach helps decouple the client code from concrete implementations and allows the system to determine the appropriate object type at runtime, improving scalability and maintainability. 🧱 Builder Pattern The Builder pattern is used when constructing complex objects that require multiple configuration steps or optional parameters. It separates the construction process from the final representation, enabling developers to build objects step by step while maintaining clean and readable code. 💡 When to Use Each Pattern • Singleton — When a single shared instance must be maintained across the application • Factory Method — When object types may vary and should be determined dynamically • Builder — When creating complex objects that require flexible and controlled construction Understanding these three creational patterns can significantly improve how developers manage object creation and design scalable, maintainable systems. #DesignPatterns #SoftwareEngineering #CleanCode #SystemDesign #OOP #Java #TechLearning

When software systems grow, the challenge is no longer writing code — it's designing code that scales. That’s where Design Patterns come in. Design patterns are proven solutions to recurring software design problems. Instead of reinventing the wheel, developers rely on patterns that improve: ✔ Flexibility ✔ Maintainability ✔ Scalability ✔ Code readability Most of the widely used patterns come from the classic book: 📘 Design Patterns: Elements of Reusable Object-Oriented Software by the Gang of Four (GoF). They introduced 23 design patterns, grouped into three categories: 🔹 Creational Patterns – How objects are created 🔹 Structural Patterns – How objects and classes are organized 🔹 Behavioral Patterns – How objects communicate These patterns are the building blocks of scalable software architecture and are widely used in frameworks, libraries, and real-world systems. In this series, I’ll break down the most practical design patterns used in real projects with simple explanations and examples. If you're learning system design, backend development, or preparing for interviews, understanding these patterns can significantly improve how you think about software architecture. #DesignPatterns #SoftwareEngineering #SystemDesign #OOP #CleanCode #Programming #BackendDevelopment #Java #Python #DotNet #SoftwareArchitecture #Developers

Why is it important to know SOLID? - Helps you write professional-quality code - Essential for real-world projects & system design - Common in technical interviews - Improves code maintainability and scalability What is Liskov Substitution Principle(LSP): - A subclass should be able to completely replace its parent class or interface without breaking the program's logic or creating any problems, and everything should still work exactly the same. Low-Level Design (LLD) of LSP for Multiple Payment Gateways - Introduced a common request (LspPaymentRequest) with a generalized field (accountIdentifier) - Makes the system flexible for different payment types (card, bKash) - No service is forced to handle unnecessary data - Clean interface; each service uses only what it needs - Both implementations work smoothly without issues Why It’s Correct: - Any child class can safely replace the parent. - No misuse of data or forced handling - Clean and flexible design - Easy to extend (supports OCP) - Maintains proper abstraction and polymorphism #LSP #LiskovSubstitutionPrinciple #SOLIDPrinciples #SOLIDDesign #ObjectOrientedProgramming #OOP #CleanCode #CleanArchitecture #SoftwareDesign #DesignPrinciples #SoftwareEngineering #BackendDevelopment #SystemDesign #ScalableSystems #CodeQuality #BestPractices #Programming #DeveloperLife #CodingStandards #DesignPatterns #Microservices #ArchitectureDesign #DomainDrivenDesign #DDD #Refactoring #MaintainableCode #ExtensibleCode #Java #SpringBoot #API #RESTAPI #TechLeadership #Developers #LearnToCode #CodingTips #SoftwareDeveloper

We have all read the clean code books. We know the rules. Keep your functions small. Abstract everything. Use interfaces. But there is a trap that almost every developer falls into, and it is called over-engineering. I have seen pull requests where a simple feature that required updating three lines of logic was turned into a massive architecture of factories, builders, and strategy patterns. You open the code to see what it does, and you have to jump through five different files just to find the actual business logic. It is theoretically clean, it is perfectly decoupled, and it is absolutely impossible to read. Clean code is not about using every design pattern you learned in a tutorial. It is about making the code easy for the next person to understand and change. Sometimes, a single function with a basic if-else statement is infinitely better than a perfectly abstracted interface with three implementations. Every abstraction you add introduces cognitive load. You are trading immediate readability for future flexibility. But nine times out of ten, that "future flexibility" is never actually needed. The business requirements change in a completely different direction, and now you are stuck maintaining a complex architecture for a use case that never happened. The real senior developer secret is knowing when to stop abstracting. Simple, slightly repetitive code is almost always better than clever, highly abstracted code. Have you ever had to untangle a massive web of "clean" code just to fix a tiny bug? Let's discuss. 👇 #SoftwareEngineering #CleanCode #Backend #SystemDesign #Coding #Programming #DeveloperLife

Stop modifying classes. Start extending them. Let’s talk about one of the most underrated features in C# 👉 Extension Methods 💡 What are Extension Methods? Extension methods allow you to add new functionality to existing classes 👉 without modifying the original code Yes… even if: You don’t own the class It’s part of a library It’s already compiled Simple Example public static class StringExtensions { public static bool IsEmail(this string value) { return value.Contains("@"); } } Now you can use it like this 👇 string email = "test@gmail.com"; bool result = email.IsEmail(); Looks like a built-in method, right? 🚀 Why Developers Love It ✔ Cleaner & readable code ✔ No need to touch existing classes ✔ Great for reusable logic ✔ Keeps your core models clean 📦 Real-World Use Cases (Modern Development) 1. Validation helpers user.Email.IsValidEmail(); 2. Formatting utilities price.ToCurrency(); 3. DTO → Entity mapping (very common in APIs) userDto.ToEntity(); 4. LINQ enhancements orders.WhereActive().OrderByDate(); ⚠️ When NOT to Use ❌ When logic is too complex ❌ When it modifies object state heavily ❌ When it hides important business logic ❌ Overusing → makes debugging harder 👉 Rule: Use for helper-like behavior, not core business rules In today’s clean architecture & microservices world: ✔ Use extension methods for: Cross-cutting concerns Shared utilities Lightweight transformations ❌ Avoid in: Domain logic Critical workflows Key Insight Extension methods are like: “Adding new powers to a class… without touching its DNA.” 🔥 Final Thought Good developers write code that works. Great developers write code that is extendable without breaking things. #csharp #dotnet #cleanarchitecture #softwaredevelopment #codingtips #backenddevelopment #webdevelopment #developers #programming #dotnetcore

Here is what I learn starting a new codebase where Cursor wrote 100% of the code; TLDR design patterns matter more than ever.