diff -r f1f852f5f477 -r e3caf3a43d09 jdk/src/java.base/share/classes/java/util/Map.java
--- a/jdk/src/java.base/share/classes/java/util/Map.java	Tue Dec 08 16:43:58 2015 -0800
+++ b/jdk/src/java.base/share/classes/java/util/Map.java	Tue Dec 08 13:48:22 2015 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2015, 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
@@ -110,6 +110,31 @@
  * Implementations may optionally handle the self-referential scenario, however
  * most current implementations do not do so.
  *
+ * <h2><a name="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.
+ * 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. Attempts to do so result in {@code UnsupportedOperationException}.
+ * 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
+ * {@code null} keys or values result in {@code NullPointerException}.
+ * <li>They are serializable if all keys and values are serializable.
+ * <li>They reject duplicate keys at creation time. Duplicate keys
+ * passed to a static factory method result in {@code IllegalArgumentException}.
+ * <li>The iteration order of mappings is unspecified and is subject to change.
+ * <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.
+ * Callers should make no assumptions about the identity of the returned instances.
+ * Factories are free to create new instances or reuse existing ones. Therefore,
+ * identity-sensitive operations on these instances (reference equality ({@code ==}),
+ * identity hash code, and synchronization) are unreliable and should be avoided.
+ * </ul>
+ *
  * <p>This interface is a member of the
  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
  * Java Collections Framework</a>.
@@ -126,7 +151,7 @@
  * @see Set
  * @since 1.2
  */
-public interface Map<K,V> {
+public interface Map<K, V> {
     // Query Operations
 
     /**
@@ -373,7 +398,7 @@
      * @see Map#entrySet()
      * @since 1.2
      */
-    interface Entry<K,V> {
+    interface Entry<K, V> {
         /**
          * Returns the key corresponding to this entry.
          *
@@ -468,7 +493,7 @@
          * @see Comparable
          * @since 1.8
          */
-        public static <K extends Comparable<? super K>, V> Comparator<Map.Entry<K,V>> comparingByKey() {
+        public static <K extends Comparable<? super K>, V> Comparator<Map.Entry<K, V>> comparingByKey() {
             return (Comparator<Map.Entry<K, V>> & Serializable)
                 (c1, c2) -> c1.getKey().compareTo(c2.getKey());
         }
@@ -485,7 +510,7 @@
          * @see Comparable
          * @since 1.8
          */
-        public static <K, V extends Comparable<? super V>> Comparator<Map.Entry<K,V>> comparingByValue() {
+        public static <K, V extends Comparable<? super V>> Comparator<Map.Entry<K, V>> comparingByValue() {
             return (Comparator<Map.Entry<K, V>> & Serializable)
                 (c1, c2) -> c1.getValue().compareTo(c2.getValue());
         }
@@ -1233,4 +1258,465 @@
         }
         return newValue;
     }
+
+    /**
+     * Returns an immutable map containing zero mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @return an empty {@code Map}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of() {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * Returns an immutable map containing a single mapping.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the mapping's key
+     * @param v1 the mapping's value
+     * @return a {@code Map} containing the specified mapping
+     * @throws NullPointerException if the key or the value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1) {
+        return Collections.singletonMap(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+    }
+
+    /**
+     * Returns an immutable map containing two mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if the keys are duplicates
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2) {
+        Map<K, V> map = new HashMap<>(3); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        if (map.size() != 2) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing three mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
+        Map<K, V> map = new HashMap<>(5); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        if (map.size() != 3) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing four mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
+        Map<K, V> map = new HashMap<>(6); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        if (map.size() != 4) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing five mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @param k5 the fifth mapping's key
+     * @param v5 the fifth mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
+        Map<K, V> map = new HashMap<>(7); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        map.put(Objects.requireNonNull(k5), Objects.requireNonNull(v5));
+        if (map.size() != 5) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing six mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @param k5 the fifth mapping's key
+     * @param v5 the fifth mapping's value
+     * @param k6 the sixth mapping's key
+     * @param v6 the sixth mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5,
+                               K k6, V v6) {
+        Map<K, V> map = new HashMap<>(9); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        map.put(Objects.requireNonNull(k5), Objects.requireNonNull(v5));
+        map.put(Objects.requireNonNull(k6), Objects.requireNonNull(v6));
+        if (map.size() != 6) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing seven mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @param k5 the fifth mapping's key
+     * @param v5 the fifth mapping's value
+     * @param k6 the sixth mapping's key
+     * @param v6 the sixth mapping's value
+     * @param k7 the seventh mapping's key
+     * @param v7 the seventh mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5,
+                               K k6, V v6, K k7, V v7) {
+        Map<K, V> map = new HashMap<>(10); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        map.put(Objects.requireNonNull(k5), Objects.requireNonNull(v5));
+        map.put(Objects.requireNonNull(k6), Objects.requireNonNull(v6));
+        map.put(Objects.requireNonNull(k7), Objects.requireNonNull(v7));
+        if (map.size() != 7) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing eight mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @param k5 the fifth mapping's key
+     * @param v5 the fifth mapping's value
+     * @param k6 the sixth mapping's key
+     * @param v6 the sixth mapping's value
+     * @param k7 the seventh mapping's key
+     * @param v7 the seventh mapping's value
+     * @param k8 the eighth mapping's key
+     * @param v8 the eighth mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5,
+                               K k6, V v6, K k7, V v7, K k8, V v8) {
+        Map<K, V> map = new HashMap<>(11); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        map.put(Objects.requireNonNull(k5), Objects.requireNonNull(v5));
+        map.put(Objects.requireNonNull(k6), Objects.requireNonNull(v6));
+        map.put(Objects.requireNonNull(k7), Objects.requireNonNull(v7));
+        map.put(Objects.requireNonNull(k8), Objects.requireNonNull(v8));
+        if (map.size() != 8) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing nine mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @param k5 the fifth mapping's key
+     * @param v5 the fifth mapping's value
+     * @param k6 the sixth mapping's key
+     * @param v6 the sixth mapping's value
+     * @param k7 the seventh mapping's key
+     * @param v7 the seventh mapping's value
+     * @param k8 the eighth mapping's key
+     * @param v8 the eighth mapping's value
+     * @param k9 the ninth mapping's key
+     * @param v9 the ninth mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5,
+                               K k6, V v6, K k7, V v7, K k8, V v8, K k9, V v9) {
+        Map<K, V> map = new HashMap<>(13); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        map.put(Objects.requireNonNull(k5), Objects.requireNonNull(v5));
+        map.put(Objects.requireNonNull(k6), Objects.requireNonNull(v6));
+        map.put(Objects.requireNonNull(k7), Objects.requireNonNull(v7));
+        map.put(Objects.requireNonNull(k8), Objects.requireNonNull(v8));
+        map.put(Objects.requireNonNull(k9), Objects.requireNonNull(v9));
+        if (map.size() != 9) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable map containing ten mappings.
+     * See <a href="#immutable">Immutable Map Static Factory Methods</a> for details.
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param k1 the first mapping's key
+     * @param v1 the first mapping's value
+     * @param k2 the second mapping's key
+     * @param v2 the second mapping's value
+     * @param k3 the third mapping's key
+     * @param v3 the third mapping's value
+     * @param k4 the fourth mapping's key
+     * @param v4 the fourth mapping's value
+     * @param k5 the fifth mapping's key
+     * @param v5 the fifth mapping's value
+     * @param k6 the sixth mapping's key
+     * @param v6 the sixth mapping's value
+     * @param k7 the seventh mapping's key
+     * @param v7 the seventh mapping's value
+     * @param k8 the eighth mapping's key
+     * @param v8 the eighth mapping's value
+     * @param k9 the ninth mapping's key
+     * @param v9 the ninth mapping's value
+     * @param k10 the tenth mapping's key
+     * @param v10 the tenth mapping's value
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any key or value is {@code null}
+     *
+     * @since 9
+     */
+    static <K, V> Map<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5,
+                               K k6, V v6, K k7, V v7, K k8, V v8, K k9, V v9, K k10, V v10) {
+        Map<K, V> map = new HashMap<>(14); // specify number of buckets to avoid resizing
+        map.put(Objects.requireNonNull(k1), Objects.requireNonNull(v1));
+        map.put(Objects.requireNonNull(k2), Objects.requireNonNull(v2));
+        map.put(Objects.requireNonNull(k3), Objects.requireNonNull(v3));
+        map.put(Objects.requireNonNull(k4), Objects.requireNonNull(v4));
+        map.put(Objects.requireNonNull(k5), Objects.requireNonNull(v5));
+        map.put(Objects.requireNonNull(k6), Objects.requireNonNull(v6));
+        map.put(Objects.requireNonNull(k7), Objects.requireNonNull(v7));
+        map.put(Objects.requireNonNull(k8), Objects.requireNonNull(v8));
+        map.put(Objects.requireNonNull(k9), Objects.requireNonNull(v9));
+        map.put(Objects.requireNonNull(k10), Objects.requireNonNull(v10));
+        if (map.size() != 10) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable 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.
+     *
+     * @apiNote
+     * It is convenient to create the map entries using the {@link Map#entry Map.entry()} method.
+     * For example,
+     *
+     * <pre>{@code
+     *     import static java.util.Map.entry;
+     *
+     *     Map<Integer,String> map = Map.ofEntries(
+     *         entry(1, "a"),
+     *         entry(2, "b"),
+     *         entry(3, "c"),
+     *         ...
+     *         entry(26, "z"));
+     * }</pre>
+     *
+     * @param <K> the {@code Map}'s key type
+     * @param <V> the {@code Map}'s value type
+     * @param entries {@code Map.Entry}s containing the keys and values from which the map is populated
+     * @return a {@code Map} containing the specified mappings
+     * @throws IllegalArgumentException if there are any duplicate keys
+     * @throws NullPointerException if any entry, key, or value is {@code null}, or if
+     *         the {@code entries} array is {@code null}
+     *
+     * @see Map#entry Map.entry()
+     * @since 9
+     */
+    @SafeVarargs
+    @SuppressWarnings("varargs")
+    static <K, V> Map<K, V> ofEntries(Entry<K, V>... entries) {
+        Map<K, V> map = new HashMap<>(entries.length * 4 / 3 + 1); // throws NPE if entries is null
+        for (Entry<K, V> e : entries) {
+            // next line throws NPE if e is null
+            map.put(Objects.requireNonNull(e.getKey()), Objects.requireNonNull(e.getValue()));
+        }
+        if (map.size() != entries.length) {
+            throw new IllegalArgumentException("duplicate keys");
+        }
+        return Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns an immutable {@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:
+     *
+     * <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()}
+     * 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>.
+     * Callers should make no assumptions about the identity of the returned instances.
+     * This method is free to create new instances or reuse existing ones. Therefore,
+     * identity-sensitive operations on these instances (reference equality ({@code ==}),
+     * identity hash code, and synchronization) are unreliable and should be avoided.
+     * </ul>
+     *
+     * @apiNote
+     * For a serializable {@code Entry}, see {@link AbstractMap.SimpleEntry} or
+     * {@link AbstractMap.SimpleImmutableEntry}.
+     *
+     * @param <K> the key's type
+     * @param <V> the value's type
+     * @param k the key
+     * @param v the value
+     * @return an {@code Entry} containing the specified key and value
+     * @throws NullPointerException if the key or value is {@code null}
+     *
+     * @see Map#ofEntries Map.ofEntries()
+     * @since 9
+     */
+    static <K, V> Entry<K, V> entry(K k, V v) {
+        // KeyValueHolder checks for nulls
+        return new KeyValueHolder<>(k, v);
+    }
 }