--- old/test/jdk/java/util/Collections/NCopies.java	2018-12-03 13:48:38.480008000 +0700
+++ new/test/jdk/java/util/Collections/NCopies.java	2018-12-03 13:48:38.120008000 +0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2018, 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
@@ -29,7 +29,9 @@
  */
 
 import java.util.Collections;
+import java.util.AbstractList;
 import java.util.List;
+import java.util.Objects;
 
 public class NCopies {
     static volatile int passed = 0, failed = 0;
@@ -81,6 +83,31 @@
             check(x.get(x.size()/2).equals("foo"));
             checkEmpty(x.subList(x.size()/2, x.size()/2));
     }
+    
+    private static <T> List<T> referenceNCopies(int n, T o) {
+        // A simplest correct implementation of nCopies to compare with the actual optimized implementation
+        return new AbstractList<>() {
+            public int size() { return n; }
+
+            public T get(int index) {
+                Objects.checkIndex(index, n);
+                return o;
+            }
+        };
+    }
+    
+    private static void checkHashCode() {
+        int[] sizes = {0, 1, 2, 3, 5, 10, 31, 32, 100, 1000};
+        String[] elements = {null, "non-null"};
+        for (int size : sizes) {
+            for (String element : elements) {
+                int expectedHashCode = referenceNCopies(size, element).hashCode();
+                int actualHashCode = Collections.nCopies(size, element).hashCode();
+                check(expectedHashCode == actualHashCode,
+                        "Collections.nCopies(" + size + ", " + element + ").hashCode()");
+            }
+        }
+    }
 
     public static void main(String[] args) {
         try {
@@ -92,6 +119,8 @@
             check(foos.size() == 42);
             checkFoos(foos.subList(foos.size()/2, foos.size()-1));
 
+            checkHashCode();
+
         } catch (Throwable t) { unexpected(t); }
 
         System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);