Code reviewMediumcr-g228

Subject DeadlocksLevel Mid–Senior~25 minCommon in Concurrency interviewsIndustries Software development

Question

Review this Java account-transfer routine.

What is the concurrency hazard, and how is it triggered?

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

1class Account {2    final Object lock = new Object();3    long balance;4}5 6void transfer(Account from, Account to, long amt) {7    synchronized (from.lock) {8        synchronized (to.lock) {        // (1)9            from.balance -= amt;10            to.balance   += amt;11        }12    }13}

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