8382196: Clean up C++ iterator style in compactHashtable.hpp and trainingData.hpp

Reviewed-by: kvn, qamai

Author: iklam

src/hotspot/share/classfile/compactHashtable.hpp

@@ -307,14 +307,9 @@ class CompactHashtable : public SimpleCompactHashtable {
   template <class ITER>
   inline void iterate(ITER* iter) const { iterate([&](V v) { iter->do_value(v); }); }
 
-  template<typename Function>
-  inline void iterate(const Function& function) const { // lambda enabled API
-    iterate(const_cast<Function&>(function));
-  }
-
   // Iterate through the values in the table, stopping when the lambda returns false.
   template<typename Function>
-  inline void iterate(Function& function) const { // lambda enabled API
+  inline void iterate(Function function) const { // lambda enabled API
     for (u4 i = 0; i < _bucket_count; i++) {
       u4 bucket_info = _buckets[i];
       u4 bucket_offset = BUCKET_OFFSET(bucket_info);

src/hotspot/share/oops/trainingData.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2025, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -217,11 +217,7 @@ class TrainingData : public Metadata {
       return *prior;
     }
     template<typename Function>
-    void iterate(const Function& fn) const { // lambda enabled API
-      iterate(const_cast<Function&>(fn));
-    }
-    template<typename Function>
-    void iterate(Function& fn) const { // lambda enabled API
+    void iterate(Function fn) const { // lambda enabled API
       return _table.iterate_all([&](const TrainingData::Key* k, TrainingData* td) { fn(td); });
     }
     int size() const { return _table.number_of_entries(); }
@@ -304,10 +300,7 @@ class TrainingData : public Metadata {
   }
 
   template<typename Function>
-  static void iterate(const Function& fn) { iterate(const_cast<Function&>(fn)); }
-
-  template<typename Function>
-  static void iterate(Function& fn) { // lambda enabled API
+  static void iterate(Function fn) { // lambda enabled API
     TrainingDataLocker l;
     if (have_data()) {
       archived_training_data_dictionary()->iterate_all(fn);