code: public static <T> Collector<T, ?, IntMomentStatistics>
  	toIntMomentStatistics(final ToIntFunction<? super T> mapper) {
  		requireNonNull(mapper);
  		return Collector.of(
  			IntMomentStatistics::new,
  			(r, t) -> r.accept(mapper.applyAsInt(t)),
  			IntMomentStatistics::combine
  		);
  	}
docs: Return a {@code Collector} which applies an int-producing mapping
  function to each input element, and returns moments-statistics for the
  resulting values.
  
  <pre>{@code
  final Stream<SomeObject> stream = ...
  final IntMomentStatistics statistics = stream
  .collect(toIntMomentStatistics(v -> v.intValue()));
  }</pre>
  
  @param mapper a mapping function to apply to each element
  @param <T> the type of the input elements
  @return a {@code Collector} implementing the moments-statistics reduction
  @throws java.lang.NullPointerException if the given {@code mapper} is
  {@code null}