diff a/src/hotspot/share/oops/flatArrayKlass.hpp b/src/hotspot/share/oops/flatArrayKlass.hpp
--- /dev/null
+++ b/src/hotspot/share/oops/flatArrayKlass.hpp
@@ -0,0 +1,153 @@
+/*
+ * Copyright (c) 2017, 2020, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_OOPS_FLATARRAYKLASS_HPP
+#define SHARE_VM_OOPS_FLATARRAYKLASS_HPP
+
+#include "classfile/classLoaderData.hpp"
+#include "oops/arrayKlass.hpp"
+#include "oops/inlineKlass.hpp"
+#include "utilities/macros.hpp"
+
+/**
+ * Array of inline types, gives a layout of typeArrayOop, but needs oops iterators
+ */
+class FlatArrayKlass : public ArrayKlass {
+  friend class VMStructs;
+
+ public:
+  static const KlassKind Kind = FlatArrayKlassKind;
+
+ private:
+  // Constructor
+  FlatArrayKlass(Klass* element_klass, Symbol* name);
+
+ public:
+
+  FlatArrayKlass() {}
+
+  virtual InlineKlass* element_klass() const;
+  virtual void set_element_klass(Klass* k);
+
+  // Casting from Klass*
+  static FlatArrayKlass* cast(Klass* k) {
+    assert(k->is_flatArray_klass(), "cast to FlatArrayKlass");
+    return (FlatArrayKlass*) k;
+  }
+
+  // klass allocation
+  static FlatArrayKlass* allocate_klass(Klass* element_klass, TRAPS);
+
+  void initialize(TRAPS);
+
+  ModuleEntry* module() const;
+  PackageEntry* package() const;
+
+  bool can_be_primary_super_slow() const;
+  GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots,
+                                                  Array<InstanceKlass*>* transitive_interfaces);
+
+  int element_byte_size() const { return 1 << layout_helper_log2_element_size(_layout_helper); }
+
+  bool is_flatArray_klass_slow() const { return true; }
+
+  bool contains_oops() {
+    return element_klass()->contains_oops();
+  }
+
+  // Override.
+  bool element_access_must_be_atomic() {
+    return element_klass()->must_be_atomic();
+  }
+
+  oop protection_domain() const;
+
+  virtual void metaspace_pointers_do(MetaspaceClosure* iter);
+
+  static jint array_layout_helper(InlineKlass* vklass); // layout helper for values
+
+  // sizing
+  static int header_size()  { return sizeof(FlatArrayKlass)/HeapWordSize; }
+  int size() const          { return ArrayKlass::static_size(header_size()); }
+
+  jint max_elements() const;
+
+  size_t oop_size(oop obj) const;
+
+  // Oop Allocation
+  flatArrayOop allocate(int length, TRAPS);
+  oop multi_allocate(int rank, jint* sizes, TRAPS);
+
+  // Naming
+  const char* internal_name() const { return external_name(); }
+
+  // Copying
+  void copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);
+
+  // GC specific object visitors
+  //
+  // Mark Sweep
+  int oop_ms_adjust_pointers(oop obj);
+
+
+  template <typename T, typename OopClosureType>
+  inline void oop_oop_iterate(oop obj, OopClosureType* closure);
+
+  template <typename T, typename OopClosureType>
+  inline void oop_oop_iterate_reverse(oop obj, OopClosureType* closure);
+
+  template <typename T, typename OopClosureType>
+  inline void oop_oop_iterate_bounded(oop obj, OopClosureType* closure, MemRegion mr);
+
+  template <typename T, class OopClosureType>
+  inline void oop_oop_iterate_elements(flatArrayOop a, OopClosureType* closure);
+
+private:
+  template <typename T, class OopClosureType>
+  inline void oop_oop_iterate_elements_specialized(flatArrayOop a, OopClosureType* closure);
+
+  template <typename T, class OopClosureType>
+  inline void oop_oop_iterate_elements_bounded(flatArrayOop a, OopClosureType* closure, MemRegion mr);
+
+  template <typename T, class OopClosureType>
+  inline void oop_oop_iterate_elements_specialized_bounded(flatArrayOop a, OopClosureType* closure, void* low, void* high);
+
+ public:
+  jint compute_modifier_flags() const;
+
+  // Printing
+  void print_on(outputStream* st) const;
+  void print_value_on(outputStream* st) const;
+
+  void oop_print_value_on(oop obj, outputStream* st);
+#ifndef PRODUCT
+  void oop_print_on(oop obj, outputStream* st);
+#endif
+
+  // Verification
+  void verify_on(outputStream* st);
+  void oop_verify_on(oop obj, outputStream* st);
+};
+
+#endif
