diff -r c5eefa465e37 -r 6ee80cd217e0 src/java.base/share/classes/java/util/Map.java
--- a/src/java.base/share/classes/java/util/Map.java	Mon Dec 04 19:49:01 2017 +0100
+++ b/src/java.base/share/classes/java/util/Map.java	Mon Dec 04 11:50:04 2017 -0800
@@ -110,17 +110,18 @@
  * Implementations may optionally handle the self-referential scenario, however
  * most current implementations do not do so.
  *
- * <h2><a id="immutable">Immutable Map Static Factory Methods</a></h2>
- * <p>The {@link Map#of() Map.of()} and
- * {@link Map#ofEntries(Map.Entry...) Map.ofEntries()}
- * static factory methods provide a convenient way to create immutable maps.
+ * <h2><a id="unmodifiable">Unmodifiable Maps</a></h2>
+ * <p>The {@link Map#of() Map.of},
+ * {@link Map#ofEntries(Map.Entry...) Map.ofEntries}, and
+ * {@link Map#copyOf Map.copyOf}
+ * static factory methods provide a convenient way to create unmodifiable maps.
  * The {@code Map}
  * instances created by these methods have the following characteristics:
  *
  * <ul>
- * <li>They are <em>structurally immutable</em>. Keys and values cannot be added,
- * removed, or updated. Calling any mutator method will always cause
- * {@code UnsupportedOperationException} to be thrown.
+ * <li>They are <a href="Collection.html#unmodifiable"><i>unmodifiable</i></a>. Keys and values
+ * cannot be added, removed, or updated. Calling any mutator method on the Map
+ * will always cause {@code UnsupportedOperationException} to be thrown.
  * However, if the contained keys or values are themselves mutable, this may cause the
  * Map to behave inconsistently or its contents to appear to change.
  * <li>They disallow {@code null} keys and values. Attempts to create them with
@@ -1276,8 +1277,8 @@
     }
 
     /**
-     * Returns an immutable map containing zero mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing zero mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1290,8 +1291,8 @@
     }
 
     /**
-     * Returns an immutable map containing a single mapping.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing a single mapping.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1307,8 +1308,8 @@
     }
 
     /**
-     * Returns an immutable map containing two mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing two mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1327,8 +1328,8 @@
     }
 
     /**
-     * Returns an immutable map containing three mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing three mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1349,8 +1350,8 @@
     }
 
     /**
-     * Returns an immutable map containing four mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing four mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1373,8 +1374,8 @@
     }
 
     /**
-     * Returns an immutable map containing five mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing five mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1399,8 +1400,8 @@
     }
 
     /**
-     * Returns an immutable map containing six mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing six mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1429,8 +1430,8 @@
     }
 
     /**
-     * Returns an immutable map containing seven mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing seven mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1461,8 +1462,8 @@
     }
 
     /**
-     * Returns an immutable map containing eight mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing eight mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1495,8 +1496,8 @@
     }
 
     /**
-     * Returns an immutable map containing nine mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing nine mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1531,8 +1532,8 @@
     }
 
     /**
-     * Returns an immutable map containing ten mappings.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * Returns an unmodifiable map containing ten mappings.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @param <K> the {@code Map}'s key type
      * @param <V> the {@code Map}'s value type
@@ -1569,9 +1570,9 @@
     }
 
     /**
-     * Returns an immutable map containing keys and values extracted from the given entries.
+     * Returns an unmodifiable map containing keys and values extracted from the given entries.
      * The entries themselves are not stored in the map.
-     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     * See <a href="#unmodifiable">Unmodifiable Maps</a> for details.
      *
      * @apiNote
      * It is convenient to create the map entries using the {@link Map#entry Map.entry()} method.
@@ -1602,15 +1603,17 @@
     @SafeVarargs
     @SuppressWarnings("varargs")
     static <K, V> Map<K, V> ofEntries(Entry<? extends K, ? extends V>... entries) {
-        if (entries.length == 0) { // implicit null check of entries
+        if (entries.length == 0) { // implicit null check of entries array
             return ImmutableCollections.Map0.instance();
         } else if (entries.length == 1) {
+            // implicit null check of the array slot
             return new ImmutableCollections.Map1<>(entries[0].getKey(),
                                                    entries[0].getValue());
         } else {
             Object[] kva = new Object[entries.length << 1];
             int a = 0;
             for (Entry<? extends K, ? extends V> entry : entries) {
+                // implicit null checks of each array slot
                 kva[a++] = entry.getKey();
                 kva[a++] = entry.getValue();
             }
@@ -1619,7 +1622,7 @@
     }
 
     /**
-     * Returns an immutable {@link Entry} containing the given key and value.
+     * Returns an unmodifiable {@link Entry} containing the given key and value.
      * These entries are suitable for populating {@code Map} instances using the
      * {@link Map#ofEntries Map.ofEntries()} method.
      * The {@code Entry} instances created by this method have the following characteristics:
@@ -1627,7 +1630,7 @@
      * <ul>
      * <li>They disallow {@code null} keys and values. Attempts to create them using a {@code null}
      * key or value result in {@code NullPointerException}.
-     * <li>They are immutable. Calls to {@link Entry#setValue Entry.setValue()}
+     * <li>They are unmodifiable. Calls to {@link Entry#setValue Entry.setValue()}
      * on a returned {@code Entry} result in {@code UnsupportedOperationException}.
      * <li>They are not serializable.
      * <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.
@@ -1655,4 +1658,30 @@
         // KeyValueHolder checks for nulls
         return new KeyValueHolder<>(k, v);
     }
+
+    /**
+     * Returns an <a href="#unmodifiable">unmodifiable Map</a> containing the entries
+     * of the given Map. The given Map must not be null, and it must not contain any
+     * null keys or values. If the given Map is subsequently modified, the returned
+     * Map will not reflect such modifications.
+     *
+     * @implNote
+     * If the given Map is an <a href="#unmodifiable">unmodifiable Map</a>,
+     * calling copyOf will generally not create a copy.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param map a {@code Map} from which entries are drawn, must be non-null
+     * @return a {@code Map} containing the entries of the given {@code Map}
+     * @throws NullPointerException if map is null, or if it contains any null keys or values
+     * @since 10
+     */
+    @SuppressWarnings({"rawtypes","unchecked"})
+    static <K, V> Map<K, V> copyOf(Map<? extends K, ? extends V> map) {
+        if (map instanceof ImmutableCollections.AbstractImmutableMap) {
+            return (Map<K,V>)map;
+        } else {
+            return (Map<K,V>)Map.ofEntries(map.entrySet().toArray(new Entry[0]));
+        }
+    }
 }