Add some suggestions for Future in UndefinedEquals.md (the actual logic was added in 1046226 but the linked documentation doesn't offer any suggestions).

java-team-github-bot · Error Prone Team · commit a9eab6084e0b · 2025-06-23T06:53:14.000-07:00
PiperOrigin-RevId: 774759018
diff --git a/docs/bugpattern/UndefinedEquals.md b/docs/bugpattern/UndefinedEquals.md
@@ -62,7 +62,14 @@ TIP: `java.util.Date` is a legacy, bug-prone API. Prefer `java.time.Instant` or
 Prefer subtypes such as `ImmutableSet` or `ImmutableList`, which have
 well-defined `equals`.
 
+## For [`Future`]
+
+Prefer calling `#get` and checking the result, or using
+`assertThat(...).isSameInstanceAs()` or `assertThat(...).isNotSameInstanceAs()`
+for cases where the same/different instance is expected.
+
 [`Collection`]: https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html
+[`Future`]: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Future.html
 [`Iterable`]: https://docs.oracle.com/javase/8/docs/api/java/lang/Iterable.html
 [`Iterables.elementsEqual`]: https://guava.dev/releases/snapshot/api/docs/com/google/common/collect/Iterables.html#elementsEqual-java.lang.Iterable-java.lang.Iterable-
 [`LinkedList`]: https://docs.oracle.com/javase/8/docs/api/java/util/LinkedList.html
