Java 21 & 25: Virtual Threads Evolution

adding more context from wiki : in Java 25, virtual threads should be used primarily for I/O-bound, high-concurrency applications to improve throughput and simplify coding style. They should be avoided for CPU-bound tasks, when using legacy libraries that cause "pinning", or when relying heavily on ThreadLocal variables for caching. When to Use Virtual Threads :::: I/O-Bound Workloads: Virtual threads excel in scenarios where tasks spend most of their time waiting for operations like network requests, database queries, or file I/O. When a virtual thread blocks on I/O, the JVM can unmount it from the underlying carrier (platform) thread, allowing the carrier thread to execute other virtual threads. High Concurrency: Use them when you need to support a large number of simultaneous connections or tasks (tens of thousands or millions). They are lightweight and have a small memory footprint, making it feasible to create one per task without running out of resources. Simplified, Blocking-Style Code: Virtual threads allow developers to write straightforward, synchronous-style code that is easy to read, debug, and maintain, avoiding the complexities of asynchronous programming (e.g., callback hell). Microservices/Web Servers: They are ideal for modern backend services and web servers that handle many client requests concurrently, improving overall throughput. When to Avoid Virtual Threads :::: CPU-Bound Tasks: Virtual threads are not intended to make code run faster on the CPU. For tasks involving intensive computation (e.g., video processing, complex data analysis), a fixed-size thread pool of platform threads, sized to the number of available CPU cores, remains the best approach. Thread Pinning Issues: Avoid them if your code frequently uses operations that "pin" the virtual thread to its carrier thread for extended periods, such as: a) synchronized blocks/methods: For frequent or long-lived locking, replace synchronized with ReentrantLock, which is designed to cooperate with virtual threads. b) Native methods (JNI) or calls into foreign functions. Heavy Reliance on ThreadLocal: ThreadLocal variables assume that a task stays on the same physical thread, which is not guaranteed with virtual threads. This can lead to subtle bugs or memory issues. Use alternatives like Scoped Values or explicit parameter passing for context propagation. Incompatible Libraries: Some older or proprietary third-party libraries (e.g., certain legacy JDBC drivers) might not be virtual-thread-aware and could cause pinning issues. Profile and test carefully when integrating such components. Low Concurrency Applications: For applications with very light loads where thread bottlenecks are not an issue, the slight overhead of the virtual thread scheduler may not provide significant

🚀☕ JAVA 26 IS OUT — AND THIS IS WHY IT MATTERS Most Java releases add features. The best ones also send a message. Java 26 does both. 👀 🔸 TL;DR Java 26 is here today. 🎉 And this release says a lot about where Java is going: ▪️ faster networking with HTTP/3 ▪️ better performance with G1 improvements ▪️ more modern concurrency ▪️ less legacy baggage ▪️ a platform that keeps getting safer and cleaner 🔸 WHAT STANDS OUT ▪️ HTTP/3 support in the HTTP Client API ▪️ G1 GC throughput improvements ▪️ Ahead-of-time object caching with any GC ▪️ Applet API finally removed ▪️ Continued progress on structured concurrency and pattern matching 🔸 THE REAL MESSAGE Java is not trying to be trendy. Java is trying to be better. Better performance. Better safety. Better foundations. Better long-term evolution. That is how serious platforms win. ⚙️ 🔸 TAKEAWAYS ▪️ Java 26 is not hype — it is momentum ▪️ Some features are still Preview/Incubator, so don’t confuse exciting with production-final ▪️ The platform keeps modernizing without losing its engineering discipline ▪️ Java’s future keeps looking stronger Java is 30+ years old. And still evolving with purpose. That’s not legacy. That’s resilience. 💪 #Java #Java26 #JDK26 #OpenJDK #JVM #Programming #SoftwareDevelopment #Backend #Concurrency #Performance See details: https://lnkd.in/ept6n2pd

Java 26 is here — and it brings some powerful upgrades! 🔹 HTTP/3 Support in HttpClient Java now supports HTTP/3, improving performance with lower latency and faster connections. Enhanced large-file streaming also allows applications to process big downloads efficiently without loading everything into memory. 🔹 Lazy Constants A safer and more flexible way to define constants. It delays initialization until needed, while still enabling JVM optimizations — improving both performance and reliability. 🔹 Virtual Thread Enhancements Virtual threads now unmount when waiting on class initialization. This improves thread scheduling and boosts efficiency in highly concurrent applications. 🔹 Ahead-of-Time Object Caching Introduces a GC-independent caching format that helps speed up application startup and warm-up times — especially useful for microservices and serverless architectures. 🔹 G1 GC Improvements G1 Garbage Collector sees throughput improvements, with reported performance gains of around 5–15% in certain workloads. 💡 Overall, Java 26 continues to push performance, scalability, and developer efficiency forward. #Java26 #Java #SoftwareDevelopment #Microservices #Performance #BackendDevelopment #tcs

The Evolution of Java Concurrency: From Platform Threads to Virtual Threads For decades, Java concurrency has relied on platform threads, which correspond one-to-one with operating system threads. While these threads are powerful, they are also resource-intensive, consuming significant memory and incurring context-switching overhead. Traditionally, backend systems managed incoming requests with carefully sized thread pools. While effective, this method limits scalability. When applications need to handle tens of thousands of concurrent tasks—especially those that block on I/O, such as database calls or network requests—threads can become a bottleneck. To address this issue, many systems have turned to asynchronous programming patterns, utilizing tools like CompletableFuture or reactive frameworks. While these approaches enhance scalability, they often increase complexity in application code. Enter virtual threads, introduced through Project Loom and available in Java 21. Unlike traditional threads, virtual threads are lightweight and scheduled by the JVM onto a smaller number of carrier threads. This innovation enables applications to manage a significantly larger number of concurrent tasks while maintaining a simple programming model. In many respects, this advancement brings Java closer to the ideal of writing straightforward blocking code while achieving massive concurrency—something that was previously challenging to accomplish efficiently. It will be interesting to observe how virtual threads continue to shape backend architecture and concurrency patterns in the coming years. #Java #Concurrency #Java21 #BackendEngineering #ProjectLoom

If you’ve worked on Java services that fan out to multiple dependencies, you probably know the real pain isn’t starting work in parallel.   It’s everything after that. One task fails. Others keep running. Cancellation becomes inconsistent. Cleanup ends up scattered across the code. The request lifecycle suddenly becomes harder to reason about than the actual business logic. That’s exactly why structured concurrency finally caught my eye. In Java 21, StructuredTaskScope gives related concurrent work one scope, one failure policy, and one cleanup boundary. It’s still a preview API, so this is not a “use it everywhere tomorrow” post. But for request-scoped orchestration, the model feels much cleaner than ad hoc futures. I just published Part 1 of a new series covering: - what structured concurrency is trying to fix   - how the Java 21 preview model works   - why join() and throwIfFailed() matter   - where it fits well, and where it does not  Article:   https://lnkd.in/gyitBUVi #Java #StructuredConcurrency #ProjectLoom #Java21 #Concurrency #BackendEngineering

Java 21 (LTS) introduces several powerful features that improve concurrency, pattern matching, and collection handling. Key highlights: • Virtual Threads – lightweight threads for high concurrency • Record Patterns – easier data extraction from records • Pattern Matching for switch – more powerful and cleaner switch statements • Sequenced Collections – better ordering support for collections • String Templates – improved string formatting • Structured Concurrency – simplified concurrent task management These features make Java more modern, scalable, and developer-friendly. Which Java 21 feature are you most excited about?

Java concurrency is changing. With Virtual Threads (Project Loom), Java can handle massive concurrency without complex thread pools. Example: ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor(); Instead of managing a pool of heavyweight threads, Java can run thousands of lightweight virtual threads. For backend services that handle lots of I/O (DB calls, APIs), this can dramatically improve scalability. Interesting to see how this reshapes Spring Boot backend architectures. #Java #SpringBoot #BackendDevelopment #SoftwareEngineering 🚀

🚀 Java Virtual Threads: The Future of Concurrency If you’ve worked with Java, you know threads are powerful… but managing them can be a headache 😅 Virtual Threads are here to change that. 💡 What are Virtual Threads? Super-lightweight threads managed by the JVM, not the OS Can run millions of tasks concurrently without eating memory Perfect for servers, APIs, and apps with high concurrency 🏃 Why they matter Traditional threads are heavy → too many threads = performance issues Virtual threads are cheap and efficient → you can focus on business logic instead of thread management 🔥 Key Benefits: ✅ Scalable – handle millions of concurrent tasks easily ✅ Efficient – less blocking, better CPU usage ✅ Readable – simpler code, fewer callbacks, cleaner architecture ⚡ Real-world impact Modern APIs and microservices can respond faster Server apps can handle more users with less hardware Developers spend less time debugging threading issues 💡 Takeaway: Virtual Threads make Java concurrency simple, fast, and scalable. For any modern Java project, they’re not just nice-to-have—they’re essential 🚀💪 #Java #CoreJava #Programming #100DaysOfCode #SoftwareDevelopment #TechInterview #JavaDeveloper

🧠 Understanding the Java Object Lifecycle In Java, every object follows a lifecycle managed by the JVM. The lifecycle begins when an object is created using the new keyword, which allocates memory for it in the heap. Once created, the object enters the active state, where it is used by the application through variables and references. As long as references to the object exist, it remains reachable and continues to serve the program. When all references are removed, the object becomes unreachable and eligible for Garbage Collection (GC). The JVM’s garbage collector then automatically removes these unused objects from memory, freeing up space and improving performance. This automatic memory management is a key reason Java is widely used in enterprise, backend, and cloud-native applications. #Java #JVM #GarbageCollection #CoreJava #JavaDeveloper #BackendDevelopment #SoftwareEngineering #ProgrammingConcepts #JavaArchitecture #JVMInternals #JavaPerformance #ObjectLifecycle

Very interesting to see that java applies Levenshtein edit distance algorithm for JVM XX flags options but not the java launcher options. Is something stopping us to do so ? jdk-25.jdk/Contents/Home/bin/java -XX:+TiereddCompilation Unrecognized VM option 'TiereddCompilation' Did you mean '(+/-)TieredCompilation'? Error: Could not create the Java Virtual Machine. Error: A fatal exception has occurred. Program will exit. YOU CAN CLEARLY SEE THE HELP. BUT HERE jdk-25.jdk/Contents/Home/bin/java -list-module Unrecognized option: -list-module Error: Could not create the Java Virtual Machine. Error: A fatal exception has occurred. Program will exit. YOU CAN"T SEE THE HELP. In the end, both are not able to create JVM, so even the launcher option can "help" us. #java25 #jdk25 #jvm #java