检查Java列表并根据某些条件创建一个新列表

Question

I have a list with "Booking" Objects . "Booking" has these attributes: - Long roomId. Date fecha. Long order. Double price.

On a certain moment, this list could be:

1 -- 22/07/2016 -- 15
1 -- 23/07/2016 -- 15
1 -- 24/07/2016 -- 15
4 -- 01/08/2016 -- 25
4 -- 02/08/2016 -- 25
4 -- 03/08/2016 -- 25
4 -- 04/08/2016 -- 25

It means, there is a Booking between July 22 and 24 for room 1, total value 45. There is a Booking between August 1 and 4 for room 4, value 100.

I want to make a new list of "OrderDetail" objects. "OrderDetail" object would have these attributes:
- roomId, InitialDate, FinalDate, price

So, with my list, It would create two OrderDetail objects and it would add to an OrderDetail list. These objects would be:

• roomId = 1, InitialDate = 22/07/2016, FinalDate = 24/07/206, price = 45
• roomId = 4, InitialDate = 01/08/2016, FinalDate = 04/08/2016, price = 100.

Could someone help me? I think it´s not a difficult code but I do not usually program so I´m having some problems to make it work.

This is my shitty code:

 L1 = (this is a database query)
L2 = (this is the same query) (so I have two identical lists)

List<OrderDetail> L3 = new ArrayList<OrderDetail>();
Long roomId = null;
Date InititalDate;
Date FinalDate;
double price = 0;

for (int i = 0; i < L1.size(); i++) {

    InititalDate = null;
    Booking current = L1.get(i);

    roomId = current.getRoomId();
    InititalDate = current.getFecha();

    Iterator<Booking> it = L2.iterator();
    while (it.hasNext()) {
        Booking current2 = it.next();
        if (current2.getRoomId.equals(roomId)) {
            precio = precio + current2.getPrecio();
            FinalDate = current2.getFecha();
            i++;
        }

    }

    OrderDetail = new OrderDetail(roomId, InitialDate, FinalDate, precio);
    L3.add(OrderDetail);

}

return L3;

}

Answer 1

I am learning Java8 , just tried to implement what you have asked, with streams

    Booking b1 = new Booking(1L, LocalDate.of(2016, 7, 22), 15d);
    Booking b2 = new Booking(1L, LocalDate.of(2016, 7, 23), 15d);
    Booking b3 = new Booking(1L, LocalDate.of(2016, 7, 24), 15d);
    Booking b4 = new Booking(4L, LocalDate.of(2016, 8, 1), 25d);
    Booking b5 = new Booking(4L, LocalDate.of(2016, 8, 2), 25d);
    Booking b6 = new Booking(4L, LocalDate.of(2016, 8, 3), 25d);
    Booking b7 = new Booking(4L, LocalDate.of(2016, 8, 4), 25d);

    List<Booking> bookings = Arrays.asList(b1, b2, b3, b4, b5, b6, b7);

    List<OrderDetail> orderDetails = bookings
            .stream().collect(Collectors.groupingBy(Booking::getRoomId)).values().stream().map(i -> new OrderDetail(i.get(0).getRoomId(),
                    i.get(0).getBookedDate(), i.get(i.size() - 1).getBookedDate(), i.stream().collect(Collectors.summingDouble(Booking::getPrice))))
            .collect(Collectors.toList());

    System.out.println(orderDetails);

output

[OrderDetail [roomId=1, startDate=2016-07-22, endDate=2016-07-24, totalPrice=45.0], OrderDetail [roomId=4, startDate=2016-08-01, endDate=2016-08-04, totalPrice=100.0]]

Please note : I believe there might be a better way of implementing this, please add your answer happy to learn from that