عرض عملي: تشخيص جمود متبادل من thread dump

خطوة بخطوة

1. Run a Shop transfer(from, to) that locks both accounts in argument order; fire opposite transfers concurrently.
2. The app hangs; take a dump with jcmd <pid> Thread.print.
3. Find the "Found one Java-level deadlock" section; read which thread holds which lock and waits for which.
4. Planned mistake: restart the app and call it solved. Fix: record the dump, identify the lock order, then fix it.
5. Apply ordered locking (lower id first) and rerun the stress test; no hang.