Code Room
Vibe codingMedium
Question
An AI wrote this Java session registry, using ConcurrentHashMap because it's thread-safe. Review whether the operations are actually safe under concurrency.
private final ConcurrentHashMap<String, Session> sessions = new ConcurrentHashMap<>(); public Session getOrCreate(String userId) { Session s = sessions.get(userId); if (s == null) { s = new Session(userId); sessions.put(userId, s); } return s;}What can go wrong despite using a concurrent map, and what's the fix?
What a strong answer looks like
Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it — tests, edge cases, reading critically — and how you’d re-prompt or decompose to get it right.
Learn the concepts
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.
Run or narrate your approach, then ask the coach.