Question

我有一份餐馆名单＆＃39;保留。我希望在一年中将它们分组，并在当天按时间排序。我怎么能用rxjava这样做？

List reservations;

class Reservation {
   public String guestName;
   public long time; //time in milliseconds
}

输出

2015年3月5日
- 预订20:00
- 预订22:00
2015年3月8日
- 预订16:00

Answer 1

要使用RxJava执行此操作，您可以先按时间（toSortedList）对列表进行排序，然后在flatMap中执行手动分组，输出Observable<List<Reservation>>，每天为您提供

Observable.from(reservations)
    .toSortedList(new Func2<Reservation, Reservation, Integer>() {
        @Override
        public Integer call(Reservation reservation, Reservation reservation2) {
            return Long.compare(reservation.time, reservation2.time);
        }
    })
    .flatMap(new Func1<List<Reservation>, Observable<List<Reservation>>>() {
        @Override
        public Observable<List<Reservation>> call(List<Reservation> reservations) {
            List<List<Reservation>> allDays = new ArrayList<>();
            List<Reservation> singleDay = new ArrayList<>();
            Reservation lastReservation = null;
            for (Reservation reservation : reservations) {
                if (differentDays(reservation, lastReservation)) {
                    allDays.add(singleDay);
                    singleDay = new ArrayList<>();
                }
                singleDay.add(reservation);
                lastReservation = reservation;
            }
            return Observable.from(allDays);
        }
    })
    .subscribe(new Action1<List<Reservation>>() {
        @Override
        public void call(List<Reservation> oneDaysReservations) {
            // You will get each days reservations, in order, in here to do with as you please.
        }
    });

我留下的differentDays方法作为读者练习。

Answer 2

由于您已经拥有完整的预订列表（即List<Reservation>，而不是Observable<Reservation>），因此您不需要RxJava - 您可以使用Java 8 stream /集合API：

Map<Calendar, List<Reservation>> grouped = reservations
    .stream()
    .collect(Collectors.groupingBy(x -> {
        Calendar cal = Calendar.getInstance();
        cal.setTimeInMillis(x.time);
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        return cal;
    }));

正如您所看到的，每年的所有工作都是groupingBy。如果您的初始数据使用Calendar而不是long作为时间戳，那么这看起来会更简单，例如：

Map<Calendar, List<Reservation>> grouped = reservations
    .stream()
    .collect(Collectors.groupingBy(x -> x.time.get(Calendar.DAY_OF_YEAR)));

按日期分组对象列表，并使用rxjava对它们进行排序

2 个答案: