code: public java.util.Optional<T> toJavaUtil() {
      return java.util.Optional.ofNullable(orNull());
    }
docs: Returns the equivalent {@code java.util.Optional} value to this optional.
  
  <p>Unfortunately, the method reference {@code Optional::toJavaUtil} will not work, because it
  could refer to either the static or instance version of this method. Write out the lambda
  expression {@code o -> o.toJavaUtil()} instead.
  
  @since 21.0