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 +1,9 @@
+Two threads, two increments, forced interleaving: read, read, write, write
+==========================================================================
+
+expected final value:                  2
+HashMap                get + put:      1
+synchronizedMap        get + put:      1
+ConcurrentHashMap      get + put:      1
+ConcurrentHashMap      merge:          2
+(each map call is individually thread-safe; the get-then-put PAIR is not atomic)