java-concurrency-reviewlisted

Review the Java code for concurrency correctness. Before reviewing, detect the Java version from `pom.xml` or `build.gradle` — suggest modern alternatives only if the version supports them. ## Step 1 — Identify concurrency primitives in use List all concurrency mechanisms found: `synchronized`, `volatile`, `AtomicXxx`, `Lock`, `ExecutorService`, `CompletableFuture`, `CountDownLatch`, `Semaphore`, `BlockingQueue`, virtual threads (Java 21+). ## Step 2 — Review for race conditions - Flag shared mutable fields accessed from multiple threads without synchronization - Flag read-modify-write operations (e.g., `count++`) not wrapped in `synchronized` or `AtomicInteger` - Flag non-atomic check-then-act patterns: `if (map.containsKey(k)) map.get(k)` → suggest `map.computeIfAbsent()` - Flag `HashMap` shared across threads → suggest `ConcurrentHashMap` - Flag `ArrayList` / `HashSet` shared across threads → suggest concurrent alternatives ## Step 3 — Review for deadlocks - Flag multiple locks acquired in inconsistent order across methods - Flag `synchronized` calls that invoke external/unknown code while holding a lock - Flag `ReentrantLock` without `try/finally` unlock → lock may never be released - Flag nested `synchronized` blocks on different objects ## Step 4 — Review synchronization granularity - Flag `synchronized` on entire methods where only a small critical section needs protection - Suggest `ReentrantLock` for fine-grained locking with timeout capability - Flag `synchroniz