125-java-concurrencylisted

# Java rules for Concurrency objects Identify and apply Java concurrency best practices to improve thread safety, scalability, and maintainability by using modern `java.util.concurrent` utilities, virtual threads, and structured concurrency. **Core areas:** Thread safety fundamentals (`ConcurrentHashMap`, `AtomicInteger`, `ReentrantLock`, `ReadWriteLock`, Java Memory Model), `ExecutorService` thread pool configuration (sizing, keep-alive, bounded queues, rejection policies, graceful shutdown), Producer-Consumer and Publish-Subscribe concurrent design patterns (`BlockingQueue`), `CompletableFuture` for non-blocking async composition (`thenApply`/`thenCompose`/`exceptionally`/`orTimeout`), immutability and safe publication (`volatile`, static initializers), lock contention and false-sharing performance optimization, virtual threads (`Executors.newVirtualThreadPerTaskExecutor()`) for I/O-bound scalability, `StructuredTaskScope` for lifecycle-scoped task management, `ScopedValue` over `ThreadLocal` for immutable cross-task data, cooperative cancellation and `InterruptedException` discipline, backpressure with bounded queues and `CallerRunsPolicy`, deadlock avoidance via global lock ordering and `tryLock` with timeouts, `ForkJoin`/parallel-stream discipline for CPU-bound work, virtual-thread pinning detection (JFR `VirtualThreadPinned`), thread naming and `UncaughtExceptionHandler` observability, and fit-for-purpose primitives (`LongAdder`, `CopyOnWriteArrayList`, `StampedLock`,