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- Samman learning hour: 5/5/10/25/5 outline; pairs stop at extracted method taking the lambda as a parameter - exercise/java: pre-factored variant of the kata (Q1/Q4 dead branch stripped, dates as constant), approval test red/flaky by design - exercise/solution: collectExpectedWeather(LongFunction<Boolean>) + no-arg overload; deterministic approval test (all-sunny lambda) - rehearse-with-agent.md: rehearsal setup with qwen + java-refactoring-mcp
51 lines
1.9 KiB
Markdown
51 lines
1.9 KiB
Markdown
# Exercise folder — Split Loop with Lambda (learning hour)
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Contents:
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- `java/` — pre-factored exercise repo (prefactored-longrange; runs with `mvn test`)
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- `solution/` — reference end state after step 3 (extracted method taking the lambda)
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- `rehearse-with-agent.md` — how Willem rehearses this with qwen-code + java-refactoring-mcp
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## Reference solution
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See `solution/`. End state of the production code (simplified):
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```java
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public Map<IceCream, Integer> longRangeForecast() {
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return longRangeForecast(daysForward -> {
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scorer.updateSelection();
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return scorer.lookupWeather(daysForward);
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});
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}
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public Map<IceCream, Integer> longRangeForecast(
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LongFunction<Boolean> dayOffsetToWeather) {
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var expectedWeather = collectExpectedWeather(dayOffsetToWeather);
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// ... reset loop + scoring loop, unchanged ...
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}
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private static List<Boolean> collectExpectedWeather(
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LongFunction<Boolean> dayOffsetToWeather) {
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var expectedWeather = new ArrayList<Boolean>();
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for (Instant interestingDate : DATES) {
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long daysForward = ChronoUnit.DAYS.between(ANCHOR_DATE, interestingDate);
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expectedWeather.add(dayOffsetToWeather.apply(daysForward));
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}
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return expectedWeather;
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}
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```
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Notes on the end state:
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- Key move: `scorer` is used **only inside the lambda**; the extracted method
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`collectExpectedWeather` has no dependency on `Scorer` at all — all its
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inputs are parameters.
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- The public no-arg overload keeps callers unchanged; it injects the
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"real" weather lambda. The test calls the overload with a pure
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`daysForward -> true` instead.
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- The test is pure and glanceable: `alwaysSunny` weather gives
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`{Strawberry:12, Chocolate:12, Vanilla:17, }` (approved file included).
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- `scorer.updateSelection()` turned out to be deletable (it only mutates
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static `Scorer.flavour` state that this method never reads). Leaving it
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in the lambda is fine for step 3; deleting it is a debrief aha.
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