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
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+8 threads x 20000 increments of one key: the atomic forms are exact on every run
+================================================================================
+
+expected:                                   160000
+ConcurrentHashMap.merge                     160000
+ConcurrentHashMap.compute                   160000
+HashMap + synchronized(map) around merge    160000