speedment/speedment

    Calendar cal = Calendar.getInstance();
    cal.set(Calendar.DAY_OF_MONTH,1);
    cal.set(Calendar.MONTH,Calendar.DECEMBER);
    cal.set(Calendar.YEAR,1998);

     java.sql.Date sqlDate = new java.sql.Date(cal.getTimeInMillis());
     LineitemManager lineitem = app.getOrThrow(LineitemManager.class);

     Map<Tuple2<String, String>, AbstractMap.SimpleEntry<Double, Double>> grouped = lineitem.stream().filter(Lineitem.L_SHIPDATE.lessOrEqual(sqlDate))
                .collect(groupingBy(t->Tuples.of(t.getLReturnflag(), t.getLLinestatus()),
                        Collectors.collectingAndThen(Collectors.toList(),
                                list-> {double first =
                                        list
                                                .stream()
                                                .mapToDouble(t -> t.getLExtendedprice().get().doubleValue()).sum();
                                    double second =
                                            list
                                                    .stream()
                                                    .collect(averagingDouble(t->t.getLTax().get().doubleValue()));

                                    return new AbstractMap.SimpleEntry<>(first, second);})
                ));


        grouped.forEach((key, value) -> System.out.println(key + ", " + value));