Summary

Describe operational semantics of Objects.equals.

Problem

A buggy equals implementation on one of its arguments can cause Objects.equals to return unexpected results.

Solution

Make the long-standing operational semantics of Objects.equals part of its specification.

Specification

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));
    }