Java Concurrency

Priority: P1 (HIGH)

Modern concurrent programming emphasizing Virtual Threads (Loom) and safety.

Implementation Guidelines

• Virtual Threads (Java 21): Use for high-throughput I/O. Executors.newVirtualThreadPerTaskExecutor().
• Structured Concurrency: Use StructuredTaskScope to treat related tasks as a 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.