如何从类返回对象，以及当构造函数创建新的HashMap时，这个对象到底是什么？

Question

我已经做了很多练习，这都有意义，但当我不得不自己从头开始编写代码时，我突然感到很困惑，如果有人能帮我一把，那就太好了。

我有：

public class Airplane {
  private HashMap<String,Integer> plane;
  public Airplane() {
    this.plane = new HashMap<String,Integer>();
  }
  public addAirplane(String id, int capacity) {
    this.plane.put(id,capacity);


 public class Flight {
   private HashMap<Airplane, List<String>> flight;
   public Flight() {
     this.flight = new HashMap<Airplane,List<String>>();
   public addFlight(Airplane airplane, String departurePort, String destinationPort) {
     this.flight.put(airplane, Arrays.asList(departurePort, destinationPort));
    }

然后我有另一个类,在这个类中创建Plane和Flight的实例,

private Airplane airplane = new Airplane();
private Flight flight = new Flight();

在大多数情况下，它似乎工作正常，但我不知道我应该在这里检索和添加什么…

flight.addFlight( //here I have Airplane's name//, departureAirport, destinationAirport);

Answer 1

好吧，我会试着解释你想要达到什么目的。看看这是不是你真正想要的。

假设您想为机场设计一个应用程序。让我们在这个时间点保持非常简单。您可以稍后为自己的用例扩展它。

让我们开始设计您的应用程序。

public class Airport {
    private List<Flight> allFlights;

    public List<Flight> getAllFlights() {
        return allFlights;
    }

    public void setAllFlights(List<Flight> allFlights) {
        this.allFlights = allFlights;
    }

    /**
     * Add flights
     * @param flight
     */
    public void addFlights(Flight flight){
        allFlights.add(flight);
    }

    /**
     * Delete flights
     * @param flight
     */
    public void deleteFlight(Flight flight){
        for(Flight eachFlight : allFlights){
            if(eachFlight.equals(flight)){
                allFlights.remove(eachFlight);
                break;
            }
        }
    }

    /**
     * Update specific flight info.
     * 
     * @param flightId
     * @param airplane
     * @param source
     * @param destination
     * @return
     */
    public boolean updateFlight(long flightId, Airplane airplane, String source, String destination){
        boolean isUpdated = false;
        for(Flight eachFlight : allFlights){
            if(eachFlight.getFlightId() == flightId){
                eachFlight.setAirplane(airplane);
                eachFlight.setSourceName(source);
                eachFlight.setDestinationName(destination);
                isUpdated = true;
                break;
            }
        }
        return isUpdated;
    }
}

每个Flight都有一个Airplane以及源和目的地Flight和Airplane只是普通的旧Java对象

public class Flight {
    private long flightId;
    private Airplane airplane;
    private String sourceName;
    private String destinationName;

    public long getFlightId() {
        return flightId;
    }

    public void setFlightId(long flightId) {
        this.flightId = flightId;
    }

    public Airplane getAirplane() {
        return airplane;
    }

    public void setAirplane(Airplane airplane) {
        this.airplane = airplane;
    }

    public String getSourceName() {
        return sourceName;
    }

    public void setSourceName(String sourceName) {
        this.sourceName = sourceName;
    }

    public String getDestinationName() {
        return destinationName;
    }

    public void setDestinationName(String destinationName) {
        this.destinationName = destinationName;
    }

    //Override equals method
}

public class Airplane {
    private long id;
    private String make;
    private String airlinesCompany;

    public Airplane(long id, String make, String airlinesCompany) {
        this.id = id;
        this.make = make;
        this.airlinesCompany = airlinesCompany;
    }

    public long getId() {
        return id;
    }

    public String getMake() {
        return make;
    }

    public String getAirlinesCompany() {
        return airlinesCompany;
    }
}

我希望这个设计能澄清你的想法。