Java

Question

我正在进行一项模拟具有天气跟踪功能的空中交通管制塔的练习。

我有一个坐标 class，它有一个私有构造函数。构造函数有 3 个参数，经度、纬度和高度。一架飞机 class 带有参数 Coordinates 坐标和名称。 aircraft class 由 3 classes JetPlane、Helicopter 和 Baloon 继承，它们的构造函数采用与 Aircraft 相同的参数。

作为练习的一部分，我必须使用工厂 class 来创建 3 个对象中的任何一个。我的问题是工厂方法将名称、类型、经度、纬度和高度作为参数，但它 returns 要求坐标对象的对象。

我如何告诉它应该从工厂 class 获取参数来制作 Coordinates 对象？我已经尝试使用 makeCoordinates 方法，但如果我将它设置为静态，则所有坐标都将为 0。有什么方法可以调用它而不是静态的并且不必创建 Coordinates 对象？

作为练习的一部分，我不允许删除或添加任何参数和访问说明符或更改它们的类型。因此 Coordinates 构造函数必须保持私有。

(Flyable是一个有注册和更新方法的接口)

这里是坐标class

public class Coordinates {
private int longitude;
private int latitude;
private int height;

public int getLongitude() {
    return longitude;
}
public void setLongitude(int longitude) {
    this.longitude = longitude;
}
public int getLatitude() {
    return latitude;
}
public void setLatitude(int latitude) {
    this.latitude = latitude;
}
public int getHeight() {
    return height;
}
public void setHeight(int height) {
    this.height = height;
}

private Coordinates(int latitude, int longitude, int height){
}

public static Coordinates makeCoordinate(int longitude, int latitude, int height) {
    return new Coordinates(longitude, latitude, height);
}

}

工厂class

public class ConcreteAircraftFactory extends AircraftFactory {

public Flyable newAircraft (String type, String name, int longitude, int latitude, int height){


    Coordinates coord = Coordinates.makeCoordinate(longitude, latitude, height);


    if (type.equals("Baloon") || type.equals("baloon")) {
        return new Baloon(name, coord);

    }

    else if(type.equals("JetPlane") || type.equals("jetplane") || type.equals("Jetplane")) {
        return new JetPlane(name, coord);

    }

    else if(type.equals("Helicopter") || type.equals("helicopter")) {
        return new Helicopter(name, coord);

    }
    else
        return null;

}

}

飞机class

public class Aircraft {

protected long  Id; 
protected String name;
protected Coordinates coordinates;
private long idCounter;

public long getId() {
    return Id;
}
public void setId(long id) {
    Id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public Coordinates getCoordinates() {
    return coordinates;
}
public void setCoordinates(Coordinates coordinates) {
    this.coordinates = coordinates;
}
public long getIdCounter() {
    return idCounter;
}
public void setIdCounter(long idCounter) {
    this.idCounter = idCounter;
}
public Aircraft( String name, Coordinates coordinates) {

    this.name = name;
    this.coordinates = coordinates;
}

private long nextId() {
    Id = getIdCounter() +1;
    idCounter++;
    return Id;
}

}

以及继承 Aircraft

的 3 个 classes 之一

public class Baloon extends Aircraft  implements Flyable {

private WeatherTower weatherTower;
private String text;

public Baloon( String name, Coordinates coordinates) {
    super( name, coordinates);
}

public void updateConditions() {
    String newWeather = weatherTower.getWeather(coordinates);


    switch(newWeather) {

    case WeatherType.FOG: 
        coordinates.setHeight(coordinates.getHeight()-3);
        text ="Baloon #" + this.getName() + "(" + this.getId() + "): get us lower, we are flying through pea soup";
        try(PrintWriter out = new PrintWriter("Simulation.txt")){
            out.println(text);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        break;

    case WeatherType.RAIN:
        coordinates.setHeight(coordinates.getHeight()-5);
        text ="Baloon #" + this.getName() + "(" + this.getId() + "): descending will not make us any less wet";
        try(PrintWriter out = new PrintWriter("Simulation.txt")  ){
            out.println(text);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        break;

    case WeatherType.SUN:
        coordinates.setHeight(coordinates.getHeight()+4);
        coordinates.setLongitude(coordinates.getLongitude()+2);
        text ="Baloon #" + this.getName() + "(" + this.getId() + "): make twoards the rising sun";
        try(PrintWriter out = new PrintWriter("Simulation.txt")  ){
            out.println(text);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        break;


    case WeatherType.SNOW:
        coordinates.setHeight(coordinates.getHeight()-15);
        text ="Baloon #" + this.getName() + "(" + this.getId() + "): this thing does not run a cold air";
        try(PrintWriter out = new PrintWriter("Simulation.txt")  ){
            out.println(text);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        break;
    }
    if(coordinates.getHeight()<0) {
        coordinates.setHeight(0);
    }
    if(coordinates.getHeight()>100) {
        coordinates.setHeight(100);
    }
    if (coordinates.getHeight()==0) {
        weatherTower.unregister(this);
        String text ="Tower Says: Baloon #" + this.getName() + "(" + this.getId() + "): has been unrergistered";
        try(PrintWriter out = new PrintWriter("Simulation.txt")  ){
            out.println(text);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

public void registerTower(WeatherTower weatherTower) {
    weatherTower.register(this);
    text ="Tower Says: Baloon #" + this.getName() + "(" + this.getId() + "): registered to weather tower";
    try(PrintWriter out = new PrintWriter("Simulation.txt")  ){
        out.println(text);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

}
}

Answer 1

实际上 Coordinates 的工厂方法调用了 Coordinates 私有构造函数，但它有一个空体。
所以它不重视 Coordinates 的任何字段：

private Coordinates(int latitude, int longitude, int height){
}

只需使用传递的参数设置当前创建的对象的字段即可：

private Coordinates(int latitude, int longitude, int height){
   this.latitude = latitude;
   this.longitude= longitude;
   this.height= height;
}

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