--- a/jdk/src/share/classes/java/awt/datatransfer/SystemFlavorMap.java	Wed Nov 13 20:16:43 2013 +0400
+++ b/jdk/src/share/classes/java/awt/datatransfer/SystemFlavorMap.java	Thu Nov 14 10:52:19 2013 +0400
@@ -40,7 +40,6 @@
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
@@ -1321,16 +1320,16 @@
     }
 
     private List<String> getAllNativesForType(String type) {
-        List<String> retval = null;
+        Set<String> retval = null;
         for (DataFlavor dataFlavor : convertMimeTypeToDataFlavors(type)) {
             List<String> natives = getFlavorToNative().get(dataFlavor);
             if (natives != null && !natives.isEmpty()) {
                 if (retval == null) {
-                    retval = new ArrayList<>();
+                    retval = new LinkedHashSet<>();
                 }
                 retval.addAll(natives);
             }
         }
-        return retval;
+        return retval == null ? null : new ArrayList<>(retval);
     }
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/awt/datatransfer/DuplicatedNativesTest/DuplicatedNativesTest.java	Thu Nov 14 10:52:19 2013 +0400
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2013, 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.
+ */
+
+import java.awt.datatransfer.DataFlavor;
+import java.awt.datatransfer.SystemFlavorMap;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+
+/* @test
+ * @bug 8028230
+ * @summary Checks that SystemFlavorMap.getNativesForFlavor returns a list without duplicates
+ * @author Petr Pchelko
+ * @run main DuplicatedNativesTest
+ */
+public class DuplicatedNativesTest {
+
+    public static void main(String[] args) throws Exception {
+
+        // 1. Check that returned natives do not contain duplicates.
+        SystemFlavorMap flavorMap = (SystemFlavorMap)SystemFlavorMap.getDefaultFlavorMap();
+        for (Map.Entry<DataFlavor, String> entry : flavorMap.getNativesForFlavors(null).entrySet()) {
+            List<String> natives = flavorMap.getNativesForFlavor(entry.getKey());
+            if (new HashSet<>(natives).size() != natives.size()) {
+                throw new RuntimeException("FAILED: returned natives contain duplicates: " + Arrays.toString(natives.toArray()));
+            }
+        }
+
+        // 2. Check that even if we set a duplicate it would be ignored.
+        flavorMap.setNativesForFlavor(DataFlavor.stringFlavor, new String[] {"test", "test", "test"});
+        List<String> natives = flavorMap.getNativesForFlavor(DataFlavor.stringFlavor);
+        if (new HashSet<>(natives).size() != natives.size()) {
+            throw new RuntimeException("FAILED: duplicates were not ignored: " + Arrays.toString(natives.toArray()));
+        }
+    }
+}