Claude
6b5a918278
gatherers/: windowFixed, windowSliding, fold, scan, mapConcurrent, a custom Gatherer (dedupeConsecutive, takeUntil), and a Collector-vs-Gatherer comparison. Verified: windowSliding emits one short window on a too-short stream rather than shrinking to empty like windowFixed; mapConcurrent waits for in-flight siblings to finish (~901ms) rather than cancelling them when one mapper throws. scoped-values/: ScopedValue API and rebinding, why plain threads (virtual or platform) do not inherit a binding while a StructuredTaskScope subtask does, and the memory cost vs InheritableThreadLocal measured two ways -- a noisy heap-delta first pass, then a precise jcmd GC.class_histogram object census (5 shared Carrier objects vs ~700,000 copied ThreadLocalMap/Entry objects for 100,000 threads). Companion code for the ankurm.com posts "Java Stream Gatherers (JEP 485)" and "Scoped Values vs ThreadLocal in Java 25: Migration Guide with Virtual Threads". Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01FtpJvZfg4nvLvtzgJTDWpB
19 lines
1.1 KiB
Plaintext
19 lines
1.1 KiB
Plaintext
$ java GathererBasics (JDK 25)
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windowFixed(3) of 1..7 = [[1, 2, 3], [4, 5, 6], [7]]
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CHECK ok : windowFixed(3) groups into [1,2,3][4,5,6][7], last window is the short remainder
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CHECK ok : windowFixed(0) throws IllegalArgumentException: 'windowSize' must be greater than zero
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windowSliding(3) of 1..5 = [[1, 2, 3], [2, 3, 4], [3, 4, 5]]
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CHECK ok : windowSliding(3) of 5 elements produces exactly 3 overlapping windows, each length 3
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CHECK ok : windowSliding(3) on a 2-element stream still emits one short window: [[1, 2]]
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CHECK ok : windowSliding(3) on an empty stream emits nothing
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fold building a String: [1][2][3][4]
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CHECK ok : fold("", acc+"[n]") over 1..4 builds "[1][2][3][4]" left to right
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CHECK ok : fold's output stream has exactly one element, the final accumulation
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scan running total of 1..5 = [1, 3, 6, 10, 15]
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CHECK ok : scan(0, +) over 1..5 emits every prefix sum: [1,3,6,10,15]
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fold(0,+) over 1..3 = [6]
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scan(0,+) over 1..3 = [1, 3, 6]
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CHECK ok : fold(0,+) over 1..3 emits just the final sum [6]
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CHECK ok : scan(0,+) over 1..3 emits every partial sum [1,3,6]
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exit=0
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