Code reviewHardcr-g198

Subject Lost updateLevel Senior–Staff~30 minCommon in Concurrency interviewsIndustries Software development

Question

Review this Java (JDBC) method that debits a wallet balance.

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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

1void withdraw(Connection conn, long acctId, BigDecimal amt) throws SQLException {2    PreparedStatement read = conn.prepareStatement(3        "SELECT balance FROM accounts WHERE id = ?");4    read.setLong(1, acctId);5    ResultSet rs = read.executeQuery();6    rs.next();7    BigDecimal bal = rs.getBigDecimal("balance");8    if (bal.compareTo(amt) < 0) throw new InsufficientFundsException();9    BigDecimal next = bal.subtract(amt);10    PreparedStatement write = conn.prepareStatement(11        "UPDATE accounts SET balance = ? WHERE id = ?");12    write.setBigDecimal(1, next);13    write.setLong(2, acctId);14    write.executeUpdate();15}

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