Added IdentityObject.newIdentity()

Author: Roger Riggs

Diff for: src/java.base/share/classes/java/lang/Object.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2020, 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
@@ -27,6 +27,8 @@
 
 import jdk.internal.HotSpotIntrinsicCandidate;
 
+import java.util.Objects;
+
 /**
  * Class {@code Object} is the root of the class hierarchy.
  * Every class has {@code Object} as a superclass. All objects,
@@ -40,6 +42,9 @@ public class Object {
 
     /**
      * Constructs a new object.
+     *
+     * @apiNote {@link Objects#newIdentity java.util.Objects.newIdentity()}
+     * should be used instead of {@code new Object()}.
      */
     @HotSpotIntrinsicCandidate
     public Object() {}

Diff for: src/java.base/share/classes/java/util/Objects.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2020, 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
@@ -436,4 +436,18 @@ int checkFromIndexSize(int fromIndex, int size, int length) {
     public static long getObjectSize(Object o) {
         return Unsafe.getUnsafe().getObjectSize(o);
     }
+
+    /**
+     * Returns a new Object implementing the {@code IdentityObject} interface.
+     * The object is a unique {@link IdentityObject} suitable for all purposes
+     * for which {@code new Object{}} was used including synchronization,
+     * mutexes and unique placeholders.
+     *
+     * @return a new Object implementing the IdentityObject interface
+     * @since Valhalla
+     */
+    public static IdentityObject newIdentity() {
+        // Return a new instance of an anonymous inner class.
+        return new IdentityObject() { };
+    }
 }