如何使用 Stream 对两个列表进行配对

Question

I have two lists:

List<Flight> flightsToCity = findFlightToCity(airport);
List<Flight> flightsFromCity = findFlightFromCity(airport);

Elements of lists are flights. I must connect every flights from list flightsToCity, with every element of second list and this must be pairs. I must do this with stream and result it must be List<Pair<Flight, Flight>> For example:

flightsToCity:

London -> Warsow,
Berlin -> Warsow

flightFromCity:

Warsow -> Barcelona,
Warsow -> Zakopane

Result:

London -> Warsow, Warsow -> Barcelona
London -> Warsow, Warsow -> Zakopane
Berlin -> Warsow, Warsow -> Barcelona
Berlin -> Warsow, Warsow -> Zakopane

Answer 1

Assuming that the lists have the same size and the elements are in the right order you could use an IntStream to solve your problem.

        List<Pair<Flight, Flight>> flightsOfAirport = IntStream
            .range(0, flightsFromCity.size())
            .mapToObj(index -> Pair.of(flightsToCity.get(index), flightsFromCity.get(index)))
            .collect(Collectors.toList());