import java.util.ArrayList;

public class Main {

    public static void main ( String[] args ) {

        FlightDatabase flightDatabase = new FlightDatabase ();{
        //    flightDatabase.checkIfFlightExists ("Wroclaw", "Berlin");

          //  flightDatabase.displayFlightsFromCity ( "Warsaw" );

        //    flightDatabase.displayFlightsToCity ( "Rotterdam" );
//
            ArrayList<String>citiesList = flightDatabase.getCities (); {
                System.out.println ( "\n" + citiesList );
            }
//            Flight cheapestFlight = flightDatabase.getCheapestFlight (); {
//                System.out.println ( "The Cheapest Flight is:" + cheapestFlight.getInfo () );
//            }
//            Flight cheapestFlightFromCity = flightDatabase.getCheapestFlightFromSpecifiedCity ( "Wroclaw" ); {
//                System.out.println ("The cheapest flight from specified city is: " + cheapestFlightFromCity.getInfo ());
//            }
            ArrayList<Flight> pathfinder = flightDatabase.getFlights ( "Wroclaw", "Vienna" );
            System.out.println ("The flight you require looks like this: " + pathfinder );



        }
    }
}
public class Flight{

    String departure;
    String arrival;
    double price;

    public Flight (String departure, String arrival, int price){
        this.departure = departure;
        this.arrival = arrival;
        this.price = price;
    }
    public String getInfo(){

        return "\n\nFlight from: " + this.departure + "\n\nFlight to: " + this.arrival +
                "\n\nPrice of this flight is: " + this.price;
    }

}
import java.util.ArrayList;

public class FlightDatabase {
    ArrayList<Flight> flights = new ArrayList<> ();

    public FlightDatabase ( ) {
        this.flights.add ( new Flight ( "Wroclaw", "Krakow", 399 ) );
        this.flights.add ( new Flight ( "Warsaw", "Poznan", 199 ) );
        this.flights.add ( new Flight ( "Krakow", "Vienna", 699 ) );
        this.flights.add ( new Flight ( "Wroclaw", "Rotterdam", 499 ) );
        this.flights.add ( new Flight ( "Warsaw", "Moscow", 999 ) );
        this.flights.add ( new Flight ( "Wroclaw", "Frankfurt", 699 ) );
        this.flights.add ( new Flight ( "Warsaw", "London", 499 ) );
        this.flights.add ( new Flight ( "Krakow", "Paris", 459 ) );
    }

    public void checkIfFlightExists ( String departure, String arrival ) {
        for (Flight check : flights) {
            if (departure.equals ( check.departure ) && arrival.equals ( check.arrival )) {
                System.out.println ( "there is such flight" );
                return;
            }
        }
        System.out.println ( "No such flight sorry" );
    }

    public ArrayList<Flight> getFlightsFromCity ( String departure ) {
        ArrayList<Flight> results = new ArrayList<> ();
        for (Flight check : this.flights) {
            if (departure.equals ( check.departure )) {
                results.add ( check );

            }
        }
        return results;
    }

    public ArrayList<Flight> getFlightsToCity ( String arrival ) {
        ArrayList<Flight> results = new ArrayList<> ();
        for (Flight check : this.flights) {
            if (arrival.equals ( check.arrival )) {
                results.add ( check );
            }
        }
        return results;
    }

    public void displayFlights ( ArrayList<Flight> results ) {
        if (results.isEmpty ()) {
            System.out.println ( "There is no such flight" );
        }
        for (Flight check : results) {
            System.out.println ( check.getInfo () );
        }
    }

    public void displayFlightsFromCity ( String departure ) {
        ArrayList<Flight> results = getFlightsFromCity ( departure );
        displayFlights ( results );
    }

    public void displayFlightsToCity ( String arrival ) {
        ArrayList<Flight> results = getFlightsToCity ( arrival );
        displayFlights ( results );
    }

    public ArrayList<String> getCities ( ) {
        ArrayList<String> cities = new ArrayList<> ();
        for (Flight check : flights) {
            if (!cities.contains ( check.arrival )) cities.add ( check.arrival );
            if (!cities.contains ( check.departure )) cities.add ( check.departure );

        }
        return cities;

    }

    public Flight getCheapestFlight ( ) {
        Flight cheapestFlight = null;
        for (Flight flight : this.flights) {
            if (cheapestFlight == null || flight.price < cheapestFlight.price) {
                cheapestFlight = flight;
            }
        }
        return cheapestFlight;
    }
    public Flight getCheapestFlightFromSpecifiedCity(String departure){
        Flight cheapestFlight = null;
        for (Flight flight: getFlightsFromCity ( departure )){
            if (cheapestFlight == null || flight.price < cheapestFlight.price){
                cheapestFlight = flight;
            }
        }
        return cheapestFlight;
    }
    public ArrayList<Flight>getFlights(String departure, String arrival){
        ArrayList<Flight>departureCity = getFlightsFromCity ( departure );
        ArrayList<Flight>arrivalCity = getFlightsToCity ( arrival );
        ArrayList<Flight>results = new ArrayList<Flight> (  );
        for (Flight first  : departureCity){
            for (Flight second : arrivalCity){
                if (first.arrival.equals ( second.departure )){
                    results.add (first);
                    results.add (second);
                }
            }
        }
        return results;
    }

}