System.out.println() Performance Impact in Java

@Autowired & @Qualifier in Spring Framework 👇 In the Spring Framework, @Autowired and @Qualifier are used for Dependency Injection. 🔹 @Autowired @Autowired is used to automatically inject dependencies into a class. The Spring IoC container finds and connects the required bean without manually creating objects using new. ✅ Why use @Autowired? Reduces boilerplate code Removes manual object creation Supports loose coupling Makes code cleaner and more readable 📌 Where can we use @Autowired? On Constructor (Recommended ✅) On Setter methods On Fields 🔹 @Qualifier @Qualifier is used along with @Autowired when multiple beans of the same type exist. It helps Spring identify which exact bean should be injected. ✅ Why use @Qualifier? Resolves ambiguity Provides better control over bean selection Makes configuration more precise 📌 Where can we use @Qualifier? In class-based (annotation-based) configuration On Constructor parameters On Setter methods On Fields 👉 In simple words: @Autowired performs injection @Qualifier selects the correct bean Together, they make Spring applications clean, flexible, and well-structured. 📚 Currently learning & implementing concepts step by step. #Spring #Autowired #Qualifier #DependencyInjection #IOC #SpringFramework #Java #BackendDevelopment #JavaFullStack #Day13_Adv_Java

🚀 Day 30/100 - Spring Boot - Handling Request Parameters When building REST APIs, handling client input correctly is key. Spring Boot provides a few powerful annotations for this 👇 ➡️ @PathVariable 🔹Binds a URL path segment to a method parameter 🔹Example: /users/{id} → @PathVariable Long id 🔹Used when the value is part of the URL itself ➡️ @RequestParam 🔹Extracts query parameters from the URL 🔹Example: /users?role=admin → @RequestParam String role 🔹Best for optional filters, search params, pagination, etc ➡️ @RequestBody 🔹Maps the request body (JSON/XML) directly to a Java object 🔹Example: JSON POST → @RequestBody User user 🔹Commonly used in POST/PUT APIs ➡️ Why this matters 🔹Clean API contracts 🔹Automatic data binding 🔹Less manual parsing 🔹Readable and maintainable code Next post: https://lnkd.in/dRHkuPyT Previous post: https://lnkd.in/da4MExJy #100Days #SpringBoot #Java #RESTAPI #PathVariable #RequestParam #RequestBody #BackendDevelopment #WebDevelopment #SoftwareEngineering

Struggling with Repeated Logging / Security Code in Spring? Let’s Talk About AOP (Aspect-Oriented Programming) In real-world Spring Boot applications, it’s common to see logging logic repeated across service methods: public void processPayment() {   System.out.println("Method started");   // business logic   System.out.println("Method ended"); } Now imagine doing this in 100 methods That’s messy. That’s repetitive. That’s hard to maintain. --> Enter AOP (Aspect-Oriented Programming) AOP helps us separate cross-cutting concerns like: ✔ Logging ✔ Security ✔ Transactions ✔ Performance monitoring from our business logic. --> Simple Example Step 1: Business Logic @Service public class PaymentService {   public void processPayment() {     System.out.println("Processing payment...");   } } Step 2: Logging Using AOP @Aspect @Component public class LoggingAspect {   @Before("execution(* com.example.service.*.*(..))")   public void logBeforeMethod(JoinPoint joinPoint) {     System.out.println("Method called: " +                joinPoint.getSignature().getName());   } } --> Output When Called: Method called: processPayment Processing payment... Notice something powerful? We didn’t touch the business code to add logging. --> How It Works Internally Spring creates a proxy object around your service. When a method is called: 👉 Proxy intercepts the call 👉 Executes the aspect (@Before) 👉 Calls the actual method Clean. Maintainable. Scalable. #SpringBoot #Java #AOP #BackendDevelopment #SoftwareEngineering #CleanCode #TechLearning

🚀 Day 2/15: Eliminating the "Billion Dollar Mistake" with Optional 🛡️ As an Architect, I see codebases cluttered with 'if (obj != null)' checks. This "defensive" coding hides the actual business logic. Today is about Java 8 Optional—the tool for cleaner, safer API design. 🧠 📝 THE "WHY": Before Java 8, returning 'null' was a silent trap. Optional<T> is a container that forces the caller to acknowledge that a value might be absent. It’s not just a wrapper; it’s an API contract. ✅ API HONESTY: Method signatures now tell the truth about potential missing data. ✅ FUNCTIONAL FLUENCY: Chain operations (.map, .filter) without nesting 'if' statements. ✅ LAZY EVALUATION: Use .orElseGet() to avoid unnecessary object creation. 🎯 MASTERING THE METHODS: 1. 🛠️ Optional.ofNullable(val): The safe way to wrap potential nulls. 2. 🔄 .flatMap(): Use this when your mapping function also returns an Optional. 3. ⚡ .orElseGet(Supplier): The "Senior" way to provide a fallback (lazy execution). 💻 IMPLEMENTATION: import java.util.Optional; public class Day2 {  public static void main(String[] args) {   String dbValue = null; // Potential null from a DB call   // The Functional, Null-Safe Approach   String result = Optional.ofNullable(dbValue)    .filter(val -> val.length() > 3)    .map(String::toUpperCase)    .orElseGet(() -> "Default Value");   System.out.println("Result: " + result);  } } 💡 INTERVIEW TIP: "Should you use Optional as a class field or method parameter?"  🚫 NO. It’s intended as a return type to help callers handle missing data. Using it as a field adds unnecessary overhead and isn't Serializable! 13 days to go! Moving from "defensive" to "expressive" code. 📈 #Java #CleanCode #Java8 #SoftwareArchitecture #Programming #Backend

I recently made a Core Java console application from scratch to rigorously practice Object-Oriented Programming and clean system design. While the application functions as a persistent Expense Tracker, my primary objective was to move beyond basic syntax and build a highly organized, maintainable codebase using enterprise-level architecture patterns. Engineering Highlights: Decoupled User Interface: Implemented the Command Pattern to isolate the CLI menu system from the underlying business logic. Loose Coupling: Utilized constructor-based Dependency Injection to manage service classes predictably. Interface-Driven Persistence: Leveraged the Strategy & Repository Patterns to create a swappable data layer, allowing the app to transition seamlessly between an In-Memory list and a persistent CSV file without altering the core services. Architecting this application solidified my command of clean code, Java design patterns, and system design principles. I would love any feedback on my repository structure from the engineering community! 🔗 https://lnkd.in/dF6jAcQn #Java #SoftwareEngineering #ObjectOrientedProgramming #CleanCode #DesignPatterns

Hi everyone 👋 📌 Spring Boot Annotation Series Part 18 – @PostMapping The @PostMapping annotation is used to handle HTTP POST requests in a Spring Boot application. It is part of the Spring Framework and is mainly used to create new resources in REST APIs. 🔹 What is @PostMapping? @PostMapping is a shortcut for: @RequestMapping(method = RequestMethod.POST) It makes the code cleaner and more readable. 🔹 When Do We Use POST? ✔ To create new data ✔ To submit form data ✔ To send request body (JSON/XML) ✔ When data is modified on the server Example use cases: Create a new user Place an order Register a customer Submit login details 🔹 Basic Example - @RestController @RequestMapping("/api/users") public class UserController { @PostMapping public String createUser(@RequestBody String user) { return "User created: " + user; } } 👉 Handles: POST http://localhost:8080/api/users 🔹 In Simple Words @PostMapping handles create operations in REST APIs. When a POST request hits the URL, Spring executes the mapped method and processes the request body. #SpringBoot #Java #RESTAPI #BackendDevelopment #InterviewPreparation #LearningInPublic

🚀 Day 9 of Advanced Java: Mastering Design Patterns & Industry Best Practices! Just completed an intensive session on Advanced Java (Day 9), diving deep into two critical #DesignPatterns that every developer should know: 🔹 Singleton Design Pattern * Ensures only one instance of a class exists in the Java Virtual Machine (JVM). * Key Implementations: Eager Loading: Object created at class loading (faster but consumes memory). Lazy Loading: Object created only when required (memory-efficient but requires synchronization for thread safety). Inner Class Optimization: Resolves lazy-loading memory wastage by initializing objects only when the inner class is called. * Real-world use: JDBC connection pools, logging frameworks, caching systems. 🔹 Factory Design Pattern * A creational pattern that delegates object creation to a centralized factory class. * Promotes polymorphism by using interfaces (e.g., Plane interface for CargoPlane, PassengerPlane). * Benefits: Decouples object creation logic from client code. Simplifies scalability (add new classes without modifying existing code). Industry standard for frameworks like Spring. 💡 Why This Matters? Design patterns aren’t just theory—they’re the backbone of scalable, maintainable, and efficient software. Understanding these concepts prepares you for real-world scenarios like: * Managing database connections (Singleton). * Building modular architectures (Factory). 🔗 Next Up: DAO (Data Access Object) Pattern—stay tuned! 👨💻 Call to Action: If you're passionate about #Java, #SoftwareDesign, or #CodingBestPractices, let’s connect! Drop a comment or DM—I’d love to discuss these patterns further. #AdvancedJava #OOP #SoftwareEngineering #Programming #Developer #TechCommunity #CodingLife #LearnInPublic #Tapacademy

Date:03/02/2026 Today reminded me that good software engineering is about clarity, not just correctness. 🔹 Problem Solved: Maximum Average Subarray While solving a sliding window problem, my logic was correct, but some test cases failed due to a subtle issue: double avg = sum / k; - ❌ integer division double avg = (double) sum / k; - ✅ correct Because both sum and k were integers, Java performed integer division first, losing decimal precision. This caused incorrect comparisons when averages were very close—especially with large inputs. Note: For fixed window the breaking logic is i-k+1 . ✔ Lesson: Even correct algorithms can fail if type behavior and precision are overlooked. 🔹 What I Learned About the Java Module System (JPMS) -> I also learned about the Java Module System (Java 9), which enforces clear boundaries in applications. A module explicitly defines: ->what it exports (public API) ->what it requires (dependencies) This metadata (module-info.java) is enforced at compile time and runtime, providing strong encapsulation and eliminating hidden dependencies. 🔹 The Common Thread ->Both experiences reinforced the same principle: ->Explicitness prevents bugs. ->Explicit casting avoids precision errors ->Explicit module boundaries avoid accidental dependencies Even though most Spring Boot apps don’t actively use JPMS, understanding it improves how I design packages, separate APIs from internals, and reason about large systems. 🎯 Takeaway Small details in code and strong boundaries in design together build reliable, scalable software. #Java #ProblemSolving #SlidingWindow #JavaModules #SoftwareEngineering #LearningJourney #BackendDevelopment

📌 Spring Boot Annotation Series – Part 8 ✅ @Component annotation The @Component annotation is used to mark a class as a Spring-managed bean 👇 🔹 Why do we use @Component? To tell Spring: 👉 “Create an object of this class and manage it.” - To enable dependency injection - To let Spring detect the class during component scanning 🔹 How does it work? When Spring Boot starts: - It scans packages (using @ComponentScan) - Finds classes annotated with @Component - Creates and registers them as beans in the Spring container 🔹 Simple example @Component public class EmailService { public void sendEmail() { System.out.println("Email sent"); } } Now this class can be injected using: @Autowired private EmailService emailService; 🔹 In simple words @Component tells Spring to automatically create and manage this class as a bean. 👉 🧠 Quick Understanding - Marks a class as a Spring bean - Detected during component scanning - Enables dependency injection #SpringBoot #Java #Component #BackendDevelopment #LearningInPublic

𝗪𝗵𝗲𝗻 𝗝𝗮𝘃𝗮 𝗙𝗲𝗲𝗹𝘀 𝗙𝗿𝗲𝘀𝗵 A few weeks ago, I was writing another class just to hold some data. Getters, setters, equals(), hashCode() etc the usual way of doing. I stopped and thought if there was a simpler way or any other way of doing this??? That’s when I started exploring some of 𝗝𝗮𝘃𝗮’𝘀 𝗺𝗼𝗱𝗲𝗿𝗻 𝗳𝗲𝗮𝘁𝘂𝗿𝗲𝘀, and they completely changed how I write code: • 𝗥𝗘𝗖𝗢𝗥𝗗𝗦: Create immutable data objects in a single line. No more endless repetitive code. • 𝗦𝗘𝗔𝗟𝗘𝗗 𝗖𝗟𝗔𝗦𝗦𝗘𝗦: Control exactly which classes can extend a parent. Safer and easier to maintain. • 𝗩𝗜𝗥𝗧𝗨𝗔𝗟 𝗧𝗛𝗥𝗘𝗔𝗗𝗦: Handle thousands of tasks concurrently without eating up memory. Lightweight and practical for high concurrency. • 𝗣𝗔𝗧𝗧𝗘𝗥𝗡 𝗠𝗔𝗧𝗖𝗛𝗜𝗡𝗚: Simplifies complex conditional logic and makes code much cleaner. So Java is not just old and reliable but with its features it keeps evolving. Using these features helps reduce routine code, write safer code, and build applications that are easier to maintain while staying in the JVM enviornment. 👉 Have you tried any of these modern Java features? Which one made the biggest difference in your projects? #Java #ModernJava #JVM #BackendDevelopment #SoftwareEngineering #Programming