code: public static <T> @Nullable Optional<T> fromJavaUtil(
        java.util.@Nullable Optional<T> javaUtilOptional) {
      return (javaUtilOptional == null) ? null : fromNullable(javaUtilOptional.orElse(null));
    }
docs: Returns the equivalent {@code com.google.common.base.Optional} value to the given {@code
  java.util.Optional}, or {@code null} if the argument is null.
  
  @since 21.0