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 +1,29 @@
+Constants read by reflection from the running JDK's own HashMap and ConcurrentHashMap
+=====================================================================================
+
+runtime: 25.0.5+8-LTS (Eclipse Adoptium)
+
+java.util.HashMap
+  DEFAULT_INITIAL_CAPACITY   = 16
+  MAXIMUM_CAPACITY           = 1073741824
+  DEFAULT_LOAD_FACTOR        = 0.75
+  TREEIFY_THRESHOLD          = 8
+  UNTREEIFY_THRESHOLD        = 6
+  MIN_TREEIFY_CAPACITY       = 64
+
+java.util.concurrent.ConcurrentHashMap
+  DEFAULT_CAPACITY           = 16
+  MAXIMUM_CAPACITY           = 1073741824
+  LOAD_FACTOR                = 0.75
+  DEFAULT_CONCURRENCY_LEVEL  = 16
+  TREEIFY_THRESHOLD          = 8
+  UNTREEIFY_THRESHOLD        = 6
+  MIN_TREEIFY_CAPACITY       = 64
+  MIN_TRANSFER_STRIDE        = 16
+  RESIZE_STAMP_BITS          = 16
+  RESIZE_STAMP_SHIFT         = 16
+  MAX_RESIZERS               = 65535
+  MOVED                      = -1
+  TREEBIN                    = -2
+  RESERVED                   = -3
+  HASH_BITS                  = 2147483647