I'm working on an exercise which simulates an air traffic control tower with weather tracking features.
I have a coordinates class which has a private constructor. The constructor takes 3 arguments, longitude, latitude and height. An aircraft class which takes with the arguments Coordinates coordinates and name. The aircraft class is inherited by 3 classes JetPlane, Helicopter and Baloon whose constructors take the same arguments as Aircraft.
As part of the exercise I have to use a factory class to create any of the 3 objects. My problem is that the factory method takes as arguments name, type, longitude, latitude and height but the objects which it returns ask for a Coordinates object.
How can I tell it that it should take the parameters from the factory class to make the Coordinates object? I have tried with a makeCoordinates method but if I set it to static that all coordinates will be 0. Is there any way to call it without it being static and without having to create a Coordinates object?
As part of the exercise I am not allowed to remove or add any parameters and access specifiers or change their type. So the Coordinates constructor will have to remain private.
(Flyable is an interface with a register and update method)
Here is the Coordinates 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);
}
}
The factory 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;
}
}
The Aircraft 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;
}
}
And one of the 3 classes which inherit Aircraft
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();
}
}
}
Actually the factory method of Coordinates invokes the Coordinates private constructor but it has an empty body.
So it doesn't value any field of Coordinates :
private Coordinates(int latitude, int longitude, int height){
}
Just set the fields of the currently created object with the passed parameters :
private Coordinates(int latitude, int longitude, int height){
this.latitude = latitude;
this.longitude= longitude;
this.height= height;
}