Planned lessonMID-004-L08

Demo: reproducing a race with a stress test

On This Lesson 3 topics

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In this lesson

prove a race exists before fixing it; prepares MID-004-LAB1.

Draft outline details

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

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