Master Java concurrency - threads, executors, locks, CompletableFuture, virtual threads

Java Concurrency Skill Master Java concurrency patterns for thread safe applications. Overview This skill covers concurrency from basic threads to virtual threads (Java 21+), including thread pools, synchronization, and CompletableFuture. When to Use This Skill Use when you need to: Write thread safe code Implement parallel processing Use async programming patterns Tune thread pools Debug concurrency issues Topics Covered Thread Management Thread lifecycle and states Daemon vs user threads Interrupt handling Synchronization synchronized, volatile Lock interfaces (ReentrantLock) Atomic operations Executors ThreadPoolExecutor configuration ForkJoinPool Virtual Threads (Java 21+) CompletableFuture Async execution Chaining and composition Exception handling Quick Reference Thread Pool Sizing Workload Formula Example CPU bound cores 8 threads I/O bound cores (1 + wait/compute) 80 threads Troubleshooting Problem Cause Solution Deadlock Circular lock Lock ordering, tryLock Race condition Missing sync Add locks/atomics Thread starvation Unfair scheduling Fair locks Debug Commands Usage

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