RFR [lworld] 8239929: Object.newIdentity() replacement for new Object()

Roger Riggs Roger.Riggs at oracle.com
Tue Feb 25 19:20:25 UTC 2020


Please review the static factory of an IdentityObject to replace "new 
Object()"
as mentioned in [1].

No replacements proposed yet.  There are 504 instances of "new Object()" 
in JDK modules.
@@ -38,15 +38,36 @@

   */
  public class Object {
  
      /**
       * Constructs a new object.
+     * @apiNote {@link Object#newIdentity} should be used instead of {@code new Object()}.
       */
      @HotSpotIntrinsicCandidate
      public Object() {}
  
      /**
+     * Constructs a new Object implementing the IdentityObject interface.
+     * The object is a unique IdentityObject suitable for all purposes
+     * that previously 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 new IdentityInstance();
+    }
+
+    /**
+     * IdentityInstance replaces plain {@code new Object()}.
+     */
+    private final static class IdentityInstance implements IdentityObject {
+        private IdentityInstance() {}
+    }
+


As a Webrev:
http://cr.openjdk.java.net/~rriggs/webrev-object-newinstance-8239929/

Thanks, Roger

[1] 
http://cr.openjdk.java.net/~briangoetz/valhalla/sov/02-object-model.html


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