code: @NotNull
      public static OptionalLong ofNullable(@Nullable Long value) {
          return value == null ? EMPTY : new OptionalLong(value);
      }
docs: Returns an {@code OptionalLong} with the specified value, or empty {@code OptionalLong} if value is null.
  
  @param value the value which can be null
  @return an {@code OptionalLong}
  @since 1.2.1