Transfer hangs between accounts

Code reviewConcurrencySenior–Staff~32 min

Review this Java account-transfer method.

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 32 min

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

1class Account {

2 private long balance;

3 final Object lock = new Object();

4 long balance() { synchronized (lock) { return balance; } }

5 void credit(long a) { synchronized (lock) { balance += a; } }

6 void debit(long a) { synchronized (lock) { balance -= a; } }

9void transfer(Account from, Account to, long amount) {

10 synchronized (from.lock) {

11 synchronized (to.lock) {

12 from.debit(amount);

13 to.credit(amount);

14 }

15 }

16}

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