Code reviewHardcr-g417

Subject DeadlocksLevel Senior–Staff~32 minCommon in Concurrency interviewsIndustries Software development, Technology

Question

Review this Java metrics registry. `record` is the hot path; it lazily creates a counter under a read lock then upgrades to write.

What a strong answer looks like

Separate real bugs from style. Rank issues by severity, point at the root cause rather than the symptom, and suggest a concrete fix — specific and kind.

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Code to reviewjava

1private final ReadWriteLock rw = new ReentrantReadWriteLock();2private final Map<String, AtomicLong> counters = new HashMap<>();3 4void record(String name) {5  rw.readLock().lock();6  if (!counters.containsKey(name)) {7    rw.writeLock().lock();          // upgrade8    counters.put(name, new AtomicLong());9    rw.writeLock().unlock();10  }11  counters.get(name).incrementAndGet();12  rw.readLock().unlock();13}

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