--- /dev/null	2018-12-03 11:58:50.256341286 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahStringDedup.hpp	2018-12-03 17:47:47.531263890 +0100
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2017, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_HPP
+
+#include "classfile/javaClasses.inline.hpp"
+#include "gc/shared/stringdedup/stringDedup.hpp"
+#include "memory/iterator.hpp"
+
+class ShenandoahStringDedup : public StringDedup {
+public:
+  // Initialize string deduplication.
+  static void initialize();
+
+  // Enqueue a string to worker's local string dedup queue
+  static void enqueue_candidate(oop java_string);
+
+  // Deduplicate a string, the call is lock-free
+  static void deduplicate(oop java_string);
+
+  static void parallel_oops_do(OopClosure* cl, uint worker_id);
+  static void oops_do_slow(OopClosure* cl);
+
+  // Parallel cleanup string dedup queues/table
+  static void parallel_cleanup();
+
+  static inline bool is_candidate(oop obj) {
+    return java_lang_String::is_instance_inlined(obj) &&
+           java_lang_String::value(obj) != NULL;
+  }
+private:
+  static void unlink_or_oops_do(BoolObjectClosure* is_alive,
+                                OopClosure* keep_alive,
+                                bool allow_resize_and_rehash);
+
+};
+
+#endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHSTRINGDEDUP_HPP