Java Multithreading Bug: A Simple Counter Example

💻 Understanding Multithreading in Java 🧵⚡ Most beginners watch multithreading… but don’t actually understand how it works internally. So today, I broke it down visually 👇 👉 In Java, multithreading allows multiple tasks to run concurrently within the same process. 👉 All threads share the same memory space, making execution faster and more efficient. 🔍 What’s happening behind the scenes? The main thread starts execution The JVM manages threads & memory Multiple threads run tasks in parallel Once completed → control returns to the main thread ⚡ Why it matters? ✔ Better CPU utilization ✔ Faster execution ✔ Improved application responsiveness 💡 Real-world use cases: Background tasks (file processing, logging) Web servers handling multiple requests Games & real-time systems 🚀 Key takeaway: Don’t just learn syntax — understand how things work under the hood. That’s what separates a coder from a developer. #Java #Multithreading #Concurrency #BackendDevelopment #100DaysOfCode #Learning #SoftwareEngineering

💻 Understanding Multithreading in Java 🧵⚡ Most beginners watch multithreading… but don’t actually understand how it works internally. So today, I broke it down visually 👇 👉 In Java, multithreading allows multiple tasks to run concurrently within the same process. 👉 All threads share the same memory space, making execution faster and more efficient. 🔍 What’s happening behind the scenes? The main thread starts execution The JVM manages threads & memory Multiple threads run tasks in parallel Once completed → control returns to the main thread ⚡ Why it matters? ✔ Better CPU utilization ✔ Faster execution ✔ Improved application responsiveness 💡 Real-world use cases: Background tasks (file processing, logging) Web servers handling multiple requests Games & real-time systems 🚀 Key takeaway: Don’t just learn syntax — understand how things work under the hood. That’s what separates a coder from a developer. #Java #Multithreading #Concurrency #BackendDevelopment #100DaysOfCode #Learning #SoftwareEngineering

🚀 Beats 100.00% of Java submissions! Just solved a LeetCode problem with 0ms runtime — faster than every other Java solution submitted. That's not something you see every day! ✅ The problem: Find the maximum product of two distinct integers in an array. Simple concept, but the key is doing it in a single O(n) pass — no sorting, no extra space. The approach: → Track the two largest numbers as you iterate → Return (first-1) × (second-1) → Done. Clean, fast, efficient. Every once in a while, the stars align and your solution hits that perfect mark. Today was that day. 💯 Keeping the momentum going — one problem at a time. 💪 #LeetCode #Java #DSA #CodingChallenge #100Percent #ProblemSolving #Programming #SoftwareEngineering #CompetitiveProgramming

Concurrent Programming: The Java Programming Language - https://lnkd.in/gSY_wqsZ Look for "Read and Download Links" section to download. Follow me if you like this post. #ConcurrentProgramming #Java #Programming #Multithreading

🚀 One Java Performance Mistake You Might Be Making Looks simple… but can hurt performance 👇 for (int i = 0; i < list.size(); i++) { System.out.println(list.get(i)); } 👉 What’s the issue? - "list.size()" is called every iteration - In some implementations, it can be costly ✅ Better approach: for (int i = 0, size = list.size(); i < size; i++) { System.out.println(list.get(i)); } OR even better 👇 for (String item : list) { System.out.println(item); } ✔ Cleaner ✔ More readable ✔ Avoids unnecessary calls 🔥 Real impact: Small optimizations matter in large-scale systems. 💡 Lesson: Write efficient loops — they run more than you think. Do you prefer traditional loops or enhanced for-loops? 👇 #Java #Performance #CodingTips #CleanCode #Developers #Programming

I just discovered Virtual Threads in Java and my mind is blown. I've been learning Java concurrency for a while now and honestly… it was painful. Thread pools. ExecutorService. CompletableFuture chains. Reactive streams. I kept thinking "there HAS to be a simpler way." Turns out… there is - Virtual Threads. Here's what blew my mind: → You can spin up MILLIONS of threads without crashing your app → You write normal, boring, sequential code… and it just scales → No more callback hell → No more guessing thread pool sizes → No more choosing between "readable" and "performant" The code went from this: CompletableFuture.supplyAsync(() -> fetchData()) .thenApply(data -> process(data)) .thenAccept(result -> save(result)) .exceptionally(ex -> handleError(ex)); To this: Thread.ofVirtual().start(() -> { var data = fetchData(); var result = process(data); save(result); }); Same result. Half the complexity. 10x more readable. I'm still learning and I'm sure there's more to it. But if you're a Java developer and you haven't looked into Virtual Threads yet, do yourself a favor and try it this weekend. #Java #LearningInPublic #VirtualThreads #Programming #SoftwareDevelopment #CodeNewbie #BackendDev

Checked Exceptions and Unchecked Exceptions may sound similar… but they behave very differently. 👀 Checked Exception is like that strict teacher: > “Handle me first, otherwise your code will not even compile.” Examples: IOException, SQLException Unchecked Exception is more dangerous: > It stays quiet… lets your program run… and then suddenly crashes everything at runtime. 💀 Examples: `NullPointerException`, `ArithmeticException` Simple rule: ✔ Checked Exception = compile-time problem ✔ Unchecked Exception = runtime surprise That’s why Java developers fear the silent ones more 😅 Which one has troubled you more? NullPointerException or IOException? #Java #CoreJava #Exceptions #CheckedException #UncheckedException #NullPointerException #JavaDeveloper #Programming #BackendDevelopment #CodingHumor

💡 A Java Mistake That Can Slow Down Your API I once wrote this inside a loop: for (User user : users) { userRepository.save(user); } It worked… but performance was terrible 👉 Problem: - Each "save()" call hits the database - Multiple round trips = slow API ❌ N database calls for N records ✅ Better approach: userRepository.saveAll(users); 🔥 Why this matters: - Reduces DB calls - Improves performance significantly - Better for bulk operations 📌 Rule: Avoid DB calls inside loops whenever possible Think in batches, not single operations. Small change. Massive performance gain. Have you optimized something like this before? 👇 #Java #SpringBoot #Programming #SoftwareEngineering #Coding #BackendDevelopment #CleanCode #Performance #TechTips

If you’re still using "𝐧𝐞𝐰 𝐓𝐡𝐫𝐞𝐚𝐝()" in Java… You’re already behind. 👇 Creating threads manually is expensive: 👉Memory overhead 👉CPU context switching 👉No control over execution And in production? 👉 It kills scalability. Modern Java solves this with the 𝐄𝐱𝐞𝐜𝐮𝐭𝐨𝐫 𝐅𝐫𝐚𝐦𝐞𝐰𝐨𝐫𝐤 Instead of creating threads: 👉 You manage 𝐭𝐡𝐫𝐞𝐚𝐝 𝐩𝐨𝐨𝐥𝐬 Why this matters: ✔ Threads are reused ✔ Better performance ✔ Controlled concurrency ✔ Safer under load But here’s where most developers go wrong: More threads ≠ faster application ❌ Too many threads lead to: 👉CPU thrashing 👉Context switching overhead 👉Performance degradation 💡 Pro rule: CPU-bound tasks → threads ≈ number of cores IO-bound tasks → can scale higher And always: 👉 𝙚𝙭𝙚𝙘𝙪𝙩𝙤𝙧.𝙨𝙝𝙪𝙩𝙙𝙤𝙬𝙣() (don’t leak resources) Concurrency isn’t about doing everything at once. It’s about doing the 𝐫𝐢𝐠𝐡𝐭 𝐭𝐡𝐢𝐧𝐠𝐬 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐭𝐥𝐲. #Java #Concurrency #Multithreading #Scalability #Backend

🚀 100 Days of Java Tips — Day 17 Tip: Avoid returning "null" from methods ❌ This is one of the most common causes of bugs in Java. Example: Bad: return null; Better: return Collections.emptyList(); ✅ Or: return Optional.empty(); ✅ Why it matters: • Reduces chances of NullPointerException • Makes your code safer • Improves readability for other developers Real problem: If someone forgets to check for null your code will crash in production ⚠️ Best practice: • Return empty collections instead of null • Use Optional for nullable values • Make your methods predictable Good code is not just working code it’s safe and reliable code Do you return null or avoid it? 👇 #Java #JavaTips #Programming #Developers #BackendDevelopment #CleanCode #SoftwareEngineering #BestPractices #Coding #Tech