Add hashmap-vs-concurrenthashmap module: JDK 25 sizeCtl/treeify internals, forced and measured lost updates

Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_017ic4b7rnC7jppGGdHGESvy
2026-10-28 18:07:37 +00:00
parent 715036b640
commit f80e1079a8
24 changed files with 958 additions and 0 deletions
@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# Regenerates every file in output/. Needs JDK 25 and Maven. First run must be online.
+# 01-04, 06-08 are written by JUnit tests that assert the same numbers (deterministic).
+# 05 is a MEASUREMENT (lost updates differ on every run) and is not asserted by any test.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+mkdir -p output
+mvn -B -q test
+mvn -B -q compile
+{ java -Xmx512m \
+    --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.util.concurrent=ALL-UNNAMED \
+    -cp target/classes com.ankurm.interviewlab.hashmapvschm.LostUpdateDemo 2>&1 \
+  | grep -v '^Picked up JAVA_TOOL_OPTIONS' ; } > output/05-measured-lost-updates.txt
+# The first line of 05 names the machine's core count; the rest varies run to run by design.
+echo "done:"; ls -1 output