--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/jdk/internal/misc/ExtendedMapMode.java	Tue Aug 20 10:11:53 2019 +0100
@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2019, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package jdk.internal.misc;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.nio.channels.FileChannel.MapMode;
+
+/**
+ * JDK-specific map modes implemented in java.base.
+ */
+public class ExtendedMapMode {
+
+    static final MethodHandle MAP_MODE_CONSTRUCTOR;
+
+    static {
+        try {
+            var lookup = MethodHandles.privateLookupIn(MapMode.class, MethodHandles.lookup());
+            var methodType = MethodType.methodType(void.class, String.class);
+            MAP_MODE_CONSTRUCTOR = lookup.findConstructor(MapMode.class, methodType);
+        } catch (Exception e) {
+            throw new InternalError(e);
+        }
+    }
+
+    public static final MapMode READ_ONLY_SYNC = newMapMode("READ_ONLY_SYNC");
+
+    public static final MapMode READ_WRITE_SYNC = newMapMode("READ_WRITE_SYNC");
+
+    private static MapMode newMapMode(String name) {
+        try {
+            return (MapMode) MAP_MODE_CONSTRUCTOR.invoke(name);
+        } catch (Throwable e) {
+            throw new InternalError(e);
+        }
+    }
+
+    private ExtendedMapMode() { }
+}