Lost update in wallet withdrawal

Code reviewConcurrencySenior–Staff~30 min

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

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.

0:00 of about 30 min

Mark a line and say what kind of problem it is.0 findings

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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