Files
javademos/scripts/gatherers.sh
T
Claude 6b5a918278 Add two standalone modules: Stream Gatherers (JEP 485) and Scoped Values vs ThreadLocal (JEP 506)
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
2026-09-24 04:27:12 +00:00

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#!/usr/bin/env bash
# Stream Gatherers (JEP 485, final since JDK 24, no preview flag needed on 25+). Every demo
# asserts its own claims (see Check.java), so a green transcript means the post's claims still
# hold on whatever JDK25 points at.
# ./scripts/gatherers.sh -> docs/output/98-basics.txt 98-mapconcurrent.txt
# 98-custom-gatherer.txt 98-collector-vs-gatherer.txt
set -uo pipefail
source "$(dirname "$0")/env.sh"
S="$ROOT/gatherers/src"; B="$ROOT/build/gatherers"; rm -rf "$B"; mkdir -p "$B"
"$JDK25/bin/javac" -d "$B" "$S"/*.java 2>&1 | grep -v -E '^(Note:|$)' || true
run() {
local outfile="$1" cls="$2"
{ echo "\$ java $cls (JDK 25)"; "$JDK25/bin/java" -cp "$B" "$cls" 2>&1; echo "exit=${PIPESTATUS[0]}"; } > "$OUT/$outfile" 2>&1
}
run 98-basics.txt GathererBasics
run 98-mapconcurrent.txt MapConcurrentDemo
run 98-custom-gatherer.txt CustomGatherer
run 98-collector-vs-gatherer.txt CollectorVsGatherer
echo "wrote $OUT/98-*.txt"