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java-concurrency

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Implement modern concurrency with Virtual Threads and Structured Concurrency in Java. Use when implementing Java Virtual Threads (Java 21), Structured Concurrency with StructuredTaskScope, CompletableFuture pipelines, or debugging race conditions.

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Java Concurrency

Priority: P1 (HIGH)

Implementation Guidelines

  • Virtual Threads (Java 21): Use for high-throughput I/O. Executors.newVirtualThreadPerTaskExecutor().
  • Structured Concurrency: Use StructuredTaskScope to treat related tasks as single unit (Scope, Fork, Join).
  • Immutability: Share immutable data between threads to avoid race conditions.
  • CompletableFuture: Use for composing async pipelines (if not using Virtual Threads).
  • Atomic Variables: Use AtomicInteger, LongAdder for simple counters.
  • Locks: Prefer ReentrantLock / ReadWriteLock over synchronized for fine-grained control.
  • Thread Safety: Document @ThreadSafe or @NotThreadSafe.

Anti-Patterns

  • No new Thread(): Use Executors or virtual threads; never create threads manually.
  • No Pooling Virtual Threads: Virtual threads cheap; never pool them.
  • No Blocking in synchronized: Pins carrier thread (Loom pitfall); use ReentrantLock instead.
  • No Shared Mutable State: Share only immutable data between threads.
  • No Thread.stop/suspend: Deprecated; use interruption or cancellation instead.

References