The methods ResponseCookie.from(...) and ResponseCookie.fromClientResponse(...) declare non-nullable String value arguments.

However, ResponseCookieBuilder.value(@Nullable String value) and DefaultResponseCookieBuilder(String name, @Nullable String value, boolean lenient) are both marked with @Nullable.

Additionally, ResponseCookie and its superclass HttpCookie allow for a null value (it is turned into an empty String).