8254880: ZGC: Let ZList iterators be alias templates

Reviewed-by: ayang, kbarrett, tschatzl

Author: pliden

src/hotspot/share/gc/z/zList.hpp

@@ -111,26 +111,8 @@ class ZListRemoveIteratorImpl : public StackObj {
   bool next(T** elem);
 };
 
-// Iterator types
-#define ZLIST_FORWARD        true
-#define ZLIST_REVERSE        false
-
-template <typename T>
-class ZListIterator : public ZListIteratorImpl<T, ZLIST_FORWARD> {
-public:
-  ZListIterator(const ZList<T>* list);
-};
-
-template <typename T>
-class ZListReverseIterator : public ZListIteratorImpl<T, ZLIST_REVERSE> {
-public:
-  ZListReverseIterator(const ZList<T>* list);
-};
-
-template <typename T>
-class ZListRemoveIterator : public ZListRemoveIteratorImpl<T, ZLIST_FORWARD> {
-public:
-  ZListRemoveIterator(ZList<T>* list);
-};
+template <typename T> using ZListIterator = ZListIteratorImpl<T, true /* Forward */>;
+template <typename T> using ZListReverseIterator = ZListIteratorImpl<T, false /* Forward */>;
+template <typename T> using ZListRemoveIterator = ZListRemoveIteratorImpl<T, true /* Forward */>;
 
 #endif // SHARE_GC_Z_ZLIST_HPP

src/hotspot/share/gc/z/zList.inline.hpp

@@ -232,16 +232,4 @@ inline bool ZListRemoveIteratorImpl<T, Forward>::next(T** elem) {
   return *elem != NULL;
 }
 
-template <typename T>
-inline ZListIterator<T>::ZListIterator(const ZList<T>* list) :
-    ZListIteratorImpl<T, ZLIST_FORWARD>(list) {}
-
-template <typename T>
-inline ZListReverseIterator<T>::ZListReverseIterator(const ZList<T>* list) :
-    ZListIteratorImpl<T, ZLIST_REVERSE>(list) {}
-
-template <typename T>
-inline ZListRemoveIterator<T>::ZListRemoveIterator(ZList<T>* list) :
-    ZListRemoveIteratorImpl<T, ZLIST_FORWARD>(list) {}
-
 #endif // SHARE_GC_Z_ZLIST_INLINE_HPP