public static void main(String[] args) {

        flights = init();
        print(flights);
        Collections.sort(flights);
        print(flights);
        List<Flight> second = filter(flights, new OriginMatcher("VIE"));
        Collections.sort(second, new DepartureComparator());
        print(second);
        System.out.printf("%d",export(flights, "filenamex"));

    }

    private static <T> java.util.List<T> filter(java.util.Collection<T> list, Matcher<T> mtch){
        List<T> filter = new LinkedList<T>();
        for(T t:list) {
            if(mtch.match(t))
                    filter.add(t);

        }
        return filter;
    }

    private static int export(java.util.List<Flight> flights, String filename) {
        int counter=0;
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter(filename+".txt"));
            for(Flight q:flights) {
                bw.write(q.toString());
                counter++;
            }
            bw.close();
        }
        catch(IOException e) {
            System.out.print("Export failed");
        }
        return counter;
    }

    private static void print(List<Flight> flights) {
        System.out.println("--- Listing Flights");
        for (Flight f : flights)
            System.out.println(f + "\n");
        System.out.printf("--- %d flights listed\n\n", flights.size());

    }


    private static List<Flight> init() {

        // ---------------- aircrafts
        List<Aircraft> crafts = new LinkedList<>();
        crafts.add(new Aircraft("A3", 3));
        crafts.add(new Aircraft("C4", 4));
        crafts.add(new Aircraft("Boeing 737", 175));

        // ---------------- passengers
        List<Passenger> passengers = new LinkedList<>();
        passengers.add(new Passenger("John", "Doe", "AT00004711"));
        passengers.add(new Passenger("Jane", "Doe", "AT00000815"));
        passengers.add(new Passenger("John", "Jackson", "US00004711"));
        passengers.add(new Passenger("Jack", "Doe", "UK00000007"));
        passengers.add(new Passenger("Jack", "Johnson", "DE00004711"));

        // ---------------- staff
        List<Staff> staff = new LinkedList<>();
        staff.add(new Staff("Rip", "Riley", "ISIS666", "Pilot"));
        staff.add(new Staff("Cheryl", "Tunt", "ISIS456", "Chef de Cabin"));
        staff.add(new Staff("Lana", "Kane", "ISIS001", "Stewardess"));

        // ---------------- flights
        List<Flight> flights = new LinkedList<>();
        flights.add(new ScheduledFlight("OS006", "FRA", "VIE", new DateTime(2018, 06, 25, 6, 30),
                new DateTime(2018, 06, 25, 8, 55), 800));
        flights.add(new Charter("OS001", "VIE", "VIE", new DateTime(2018, 06, 23, 6, 30),
                new DateTime(2018, 06, 23, 8, 55)));
        flights.add(new Charter("OS381", "ARN", "VIE", new DateTime(2018, 05, 25, 6, 30),
                new DateTime(2018, 05, 25, 9, 13)));
        flights.add(new Charter("OS001", "VIE", "JFK", new DateTime(2018, 07, 25, 4, 30),
                new DateTime(2018, 07, 25, 7, 20)));
        flights.add(new Charter("OS502", "JFK", "VIE", new DateTime(2018, 06, 28, 18, 30),
                new DateTime(2018, 06, 28, 19, 55)));
        flights.add(new ScheduledFlight("OS007", "VIE", "CDG", new DateTime(2018, 06, 28, 21, 00),
                new DateTime(2018, 06, 29, 0, 05), 1000));
        flights.add(new ScheduledFlight("OS008", "VIE", "CDG", new DateTime(2018, 06, 1, 6, 30),
                new DateTime(2018, 06, 1, 8, 05), 1000));


        Flight f;

        // ---------------- set up flight
        f = flights.get(0).setVessel(crafts.get(0));
        f.add(staff.get(0));
        f.add(staff.get(1));
        f.add(staff.get(2));
        // list passengers
        f.add(passengers.get(0));
        f.add(passengers.get(1));
        f.add(passengers.get(2));
        f.add(passengers.get(3)); //exceeds vessel capacity
        // board passengers
        f.board(passengers.get(0)); // board listed passengers
        f.board(passengers.get(1));
        f.board(passengers.get(2));
        f.board(passengers.get(3)); // board a passenger not listed


        // ---------------- set up flight
        f = flights.get(1).setVessel(crafts.get(1));
        f.add(passengers.get(1));
        f.add(passengers.get(2));
        f.add(passengers.get(3));
        f.add(new Staff(passengers.get(0), "Pilot"));  //a passenger becomes a pilot
        f.board(passengers.get(1)); // already on board another flight
        f.board(passengers.get(3)); // board a passenger



        // ---------------- set up flight
        f = flights.get(2).setVessel(crafts.get(2));
        Passenger p = new Passenger(staff.get(0)); //staff becomes a passenger
        f.add(passengers.get(2));
        f.add(passengers.get(1));
        f.add(passengers.get(3));
        f.add(p);
        f.board(p); //no boarding without crew


        // ---------------- set up flight
        f = flights.get(3);
        f.add(passengers.get(2));
        f.add(passengers.get(1));
        f.add(passengers.get(3));


        // ---------------- set up flight
        f = flights.get(4);
        f.add(passengers.get(2));
        f.add(passengers.get(1));
        f.add(passengers.get(3));

        // ---------------- set up flight
        f = flights.get(5);
        f.add(passengers.get(2));
        f.add(passengers.get(1));
        f.add(passengers.get(3));

        return flights;
    }

}

import java.util.Set;
import java.util.TreeSet;


public abstract class Flight implements Comparable<Flight> {

    private DateTime arrival;
    private java.util.Set<Staff> crew;
    private DateTime departure;
    private String destination;
    private String flightID;
    private String origin;
    private java.util.Set<Passenger> passengers;
    private Aircraft vessel;

    public Flight(Flight f) {
        this.setFlightID(f.flightID);
        this.setArrival(new DateTime(arrival));
        this.setDeparture(new DateTime(departure));
        this.setDestination(f.destination);
        this.setOrigin(f.origin);
    }

    public void setDestination(String destination) throws IllegalArgumentException {
        if (destination != null && destination != "")
            this.destination = destination;
        else
            throw new IllegalArgumentException("please enter valid destination");
    }

    public abstract int getBonusMiles();

    public int compareTo(Flight o) {
        return this.getFlightID().compareTo(o.getFlightID());
    }

    public boolean add(Staff Staff) {
        return crew.add(Staff);
        // crew.remove(Staff);
    }
    public boolean board(Passenger p) {
        if(this.readyToBoard()) {
            if(this.passengers.contains(p) && p.getBoarded()== null)
                return true;
        }
        return false;
    }

    public boolean readyToBoard() {
        if(this.crew.size() > 0)
        return true;
        else
            return false;
    }
    public boolean boardingCompleted() {

        if(this.passengers.size()>0) {
            boolean check = true;
            for(Passenger p:passengers) {
                if (p.getBoarded()!=this) {
                    check = false;
                }
            }
            return check;
        }
        return false;
    }

    public void setOrigin(String origin) throws IllegalArgumentException {
        if (origin != null && origin != "")
            this.origin = origin;
        else
            throw new IllegalArgumentException("please enter valid origin");
    }


    public Flight(DateTime arrival, DateTime departure, String destination, String flightID, String origin) {
        super();
        this.arrival = arrival;
        this.departure = departure;
        this.destination = destination;
        this.flightID = flightID;
        this.origin = origin;
        this.passengers = passengers;
    }

    private final String ensureNonNullNonEmpty(String str) throws IllegalArgumentException {
        if (str != null && str != "")
            return str;
        else {
            throw new IllegalArgumentException("Illegal Argument!");
        }
    }

    @Override
    public String toString() {
        return String.format(
                "%5s from %3.3S (%s) to %3.3S (%s)" + " with a crew of %d and %d passengers "
                        + "<%s> boarding%scompleted \n%s\n%s",
                flightID, origin, departure, destination, arrival, crew == null ? 0 : crew.size(),
                passengers == null ? 0 : passengers.size(), vessel == null ? "no vessel" : vessel.toString(),
                boardingCompleted() ? " " : " not ", crew, passengers);
    }

}