JDK 13 RFR of JDK-8223112: Clarify operational semantics of java.util.Objects.equals()

[Joe Darcy]

Hello,

Bug JDK-8223112 notes indirectly that if Objects.equals is called with 
(foo, null) and foo has a buggy equals method that returns true for 
null, the wrong result will be computed.

I don't think code should be added to Objects.equals itself to guard 
against this case. Instead, I think the operational semantics of the 
implementation should be made explicit in the specification.

Please review the patch below.

Thanks,

-Joe

diff -r 7ab4310ed472 src/java.base/share/classes/java/util/Objects.java
--- a/src/java.base/share/classes/java/util/Objects.java    Wed May 01 
20:25:31 2019 -0700
+++ b/src/java.base/share/classes/java/util/Objects.java    Thu May 02 
14:41:06 2019 -0700
@@ -62,10 +62,11 @@
       * Returns {@code true} if the arguments are equal to each other
       * and {@code false} otherwise.
       * Consequently, if both arguments are {@code null}, {@code true}
-     * is returned and if exactly one argument is {@code null}, {@code
-     * false} is returned.  Otherwise, equality is determined by using
-     * the {@link Object#equals equals} method of the first
-     * argument.
+     * is returned.  Otherwise, if the first argument is not {@code
+     * null}, equality is determined by calling the {@link
+     * Object#equals equals} method of the first argument with the
+     * second argument of this method. Otherwise, {@code false} is
+     * returned.
       *
       * @param a an object
       * @param b an object to be compared with {@code a} for equality

...

     public static boolean equals(Object a, Object b) {
         return (a == b) || (a != null && a.equals(b));
     }