عرض عملي: إعادة إنتاج حالة تسابق باختبار إجهاد

خطوة بخطوة

1. Write StockCounter with reserve(int) using check-then-act.
2. Stress test: 100 threads each reserve 1 unit from 1,000, started together with a CountDownLatch; assert final stock is 900.
3. Run repeatedly; the test fails intermittently (stock above 900, or oversold).
4. Planned mistake: add volatile to the field and re-run; it still fails. Explain: visibility is not atomicity.
5. Fix with synchronized; the test passes across many runs.
6. Note that a passing run is evidence only when the test failed before the fix.