Spring IoC Container: How it Works and Benefits

I recently encountered an ambiguous mapping error while working on a REST API. The stack trace was overwhelming, but the message was straightforward : I had two different methods competing for the same URL and HTTP verb. The issue happened because I had two methods, createEmployee and createNewEmployee, both annotated with @PostMapping, along with @RequestMapping on the controller class. Spring couldn't determine which method to use to handle the request. To resolve this, it's essential to keep the endpoints unique or utilize different HTTP methods to maintain organization. Happy coding! #Java #SpringBoot #Programming #SoftwareEngineering #Debugging

💫@𝐏𝐫𝐢𝐦𝐚𝐫𝐲 𝐯𝐬 @𝐐𝐮𝐚𝐥𝐢𝐟𝐢𝐞𝐫 𝐢𝐧 𝐒𝐩𝐫𝐢𝐧𝐠 𝐁𝐨𝐨𝐭: When working with dependency injection in Spring Boot, handling multiple beans of the same type can get tricky. That’s where @Primary and @Qualifier come into play 👇 👉 @Primary Used to define a default bean. If multiple beans exist, Spring automatically picks the one marked as @Primary. 👉 @Qualifier Used to explicitly specify which bean you want. Gives you precise control over dependency injection. 💡 Key Insight: Use @Primary for default behavior and @Qualifier when you need specific control. Together, they make your code more flexible and maintainable. #SpringBoot #JavaDeveloper #BackendDevelopment #DependencyInjection #SpringFramework #Java #Coding #SoftwareDevelopment #TechLearning #Developers #Programming #100DaysOfCode #JavaBackend #SpringAnnotations 𝐓𝐡𝐚𝐧𝐤𝐬 𝐭𝐨 𝐦𝐲 𝐌𝐞𝐧𝐭𝐨𝐫: Anand Kumar Buddarapu Saketh Kallepu Uppugundla Sairam

Find the minimum distance between a given start index and any occurrence of a target in the array. Leetcode problem link: https://lnkd.in/gZFkirHw 🔍 Key Takeaways: Used a two-pointer approach to scan from both ends. Kept updating the minimum absolute distance from start. Included the condition left != right to avoid checking the same element twice. ✅ Why this works: Instead of scanning only from one side, this approach checks both ends in each iteration, making the logic structured and efficient. 📘 What I like about this solution: Simple and readable Avoids redundant checks Great example of combining two pointers with distance calculation #Java #LeetCode #DSA #Programming #SoftwareEngineering #Developers #loveToCode

Day 45-What if your entire application depended on just one object… and creating more could break things? That’s exactly why Singleton Class exists. 🔹 What is a Singleton Class? A Singleton class ensures that 👉 only one object is created in the entire application. No matter how many times you access it, you always get the same instance. 🔹 How is it implemented? • Make the constructor private → restrict object creation • Create a static reference → hold the single instance • Provide a public static method → return that instance 🔹 Types of Singleton 1. Lazy Initialization 👉 Object is created only when required ✔ Saves memory ✔ Efficient for large applications 2. Eager Initialization 👉 Object is created when the class is loaded ✔ Simple and fast ✔ Always ready to use 🔹 Why does Singleton matter? • Prevents unnecessary object creation • Maintains consistency • Saves memory • Useful for shared resources like: DB connections, logging, configurations 🔹 Key takeaway 👉 Control object creation → Control your application behavior #Java #OOP #Singleton #DesignPatterns #JavaProgramming #Coding #SoftwareDevelopment #Developers #TechLearning #100DaysOfCode #Programming #CodeSmart #BackendDevelopment

🚀 Day 559 of #750DaysOfCode 🚀 🔍 LeetCode 3741: Minimum Distance Between Three Equal Elements II Today’s problem was an extension of yesterday’s question — but with larger constraints (n up to 1e5), making efficiency crucial ⚡ 💡 Problem Recap: Find three indices (i, j, k) such that: nums[i] == nums[j] == nums[k] Distance = |i - j| + |j - k| + |k - i| is minimized ✨ Approach I Used (Clean & Intuitive): ✔ Stored indices of each number using a HashMap ✔ For each number: If it appears ≥ 3 times Check consecutive triplets of indices ✔ Compute distance using: 👉 |i - j| + |j - k| + |k - i| 💻 Key Code Insight: Instead of checking all combinations, I only checked sliding windows of size 3 within index lists — reducing unnecessary work. 🧠 Learning: Even in medium problems, a simple structured approach (grouping + sliding window) can pass efficiently when applied correctly. ⚡ Complexity: Time: O(n) to build map + O(n) traversal Space: O(n) 💬 Takeaway: Don’t overcomplicate — sometimes the same idea from an easy problem scales well with just a small optimization in thinking. #LeetCode #DSA #Java #CodingJourney #ProblemSolving #Tech #Programming #Developers #100DaysOfCode

🚀 Understanding @Primary vs @Qualifier in Spring Boot While working with Spring, one common confusion I faced was handling multiple beans of the same type. Here’s a simple breakdown 👇 🔹 @Primary Used when you want to mark one bean as the default choice If multiple beans are available, Spring will pick the one marked with @Primary 🔹 @Qualifier Used when you want to explicitly specify which bean to use Helps avoid ambiguity when multiple beans exist 💡 Example Scenario: If you have two implementations of the same interface: Use @Primary → when one is commonly used Use @Qualifier → when you need a specific one ✅ Key Difference: @Primary → Default selection @Qualifier → Specific selection 🎯 Best Practice: Use @Qualifier when you need control, and @Primary when you have a clear default. Understanding this helps in writing clean, maintainable, and flexible Spring applications 💻 #Java #SpringBoot #BackendDevelopment #Programming #Developers #Learning #Coding

🚀 Day 15 of 180 — 3Sum Closest ✅ LeetCode 16 — 3Sum Closest First sort the array. Then fix one element and use two pointers for the remaining two — one at left, one at right. For every triplet I calculate the sum and check how far it is from the target: distance = |target - sum| If this distance is less than my current minimum difference, I update my answer. Moving pointers is simple — if sum is greater than target → move right pointer left if sum is less than target → move left pointer right if sum equals target → that's the closest it can get, return immediately The key thing I made sure — keep tracking the minimum difference throughout and update result whenever a closer sum is found. Day 15 done. 165 to go. 🔥 #180DaysDSA #Day15 #LeetCode #Java #DSA #TwoPointers #Sorting #ThreeSum #DSAJourney #CodingJourney #Programming #DataStructures #Algorithms #ProblemSolving #BuildInPublic #CodeNewbie #LearnToCode #100DaysOfCode #SoftwareDevelopment #Developer #StudentDeveloper #TechCommunity #LinkedInTech #CompetitiveProgramming

What happened when run the code ? @RestController public class TestController { @Autowired private TestService testService; public TestController() { System.out.println(testService.getMessage()); } } Looks correct but throw error ? Answer: NullPointerException Why : spring inject dependencies after constructer execution so testService is null inside constructer #Spring flow is: 1. Object is created (constructor runs first) 2. Then dependency injection happens (@Autowired) #SpringBoot #Java #Backend #CodingInterview #FAANG #Microservices #Programming #Developers

Headline: Why stop at 15 digits? 🚀 I’ve always found it frustrating when standard calculators hit a limit and switch to scientific notation or simply give up. Whether it’s massive factorials or high-precision cryptography values, shouldn't our tools be able to handle "the big stuff"? To solve this, I built Calculator-infinite — a tool designed to process numbers of any length without losing precision. What makes this different? Unlike standard data types that have a fixed bit-size, this project uses logic to handle numbers as strings, meaning the only limit to your calculation is your computer's memory. I’m looking for your feedback! I want to push this further and would love for the dev community to break it. How does it handle your most complex strings? What features should I add next (Advanced functions? A GUI?)? Check out the logic here: https://lnkd.in/gwmT7hW5 If you enjoy tinkering with algorithms or just want to see how deep the rabbit hole goes with "Infinite" math, take a look at the repo. Stars, forks, and honest critiques are all welcome! #OpenSource #JavaScript #Coding #WebDevelopment #DataStructures #Programming #Mathematics #GitHub