我无法使用 super() 在子类中的超类之外创建 2 个对象；

Question

I have a Superclass 'Telefoon' (english: Telephone). this superclass has a child/subclass 'ContactGegevens' (Egnlish Contact data/user Information). This subclass 'ContactGegevnes' is a superclass of a child/subclass as well but is not relevant for my question.

In Super class 'Telefoon' (Telephone).

public class Telefoon {

//Properties.
private String soort; //Enlgish = Type (Mobile or landline)
private String nummer; //English = Number (Just the number).

//Getters and Setters.
//Just normal getters and setters of all properties. not relevant to show here.    

//Constructors.
public Telefoon(String soort, String nummer) {
    this.nummer = nummer;
    this.soort = soort;
}

/** This constructor does nothing but when I don't have this one it gives and error in the child 
class??? */
public Telefoon() {
    this.nummer = "000000000";
    this.soort = "vast";
}

//Methods.
//Not relevant for question.

Child/Subclass 'ContactGegevens'.

public class ContactGegevens extends Telefoon {

//Properties.
private String eMail;         //Email.
private Telefoon telefoon;    //Landline number.
private Telefoon gsm;         //Mobile phone number.

//Getters and Setters.
//Getters and Setters of all 3 properties. irrelevant to show here

//Constructors.
public ContactGegevens(String vast, String mobiel, String eMail) {
    /**
    *This works but in this case the 'extends Telefoon' is useless???!!
    As you can see I create 2 objects of superClass Telefoon. But then the 'extends Telefoon'
    is unnecessary, is there a Way i can do something like 

    telefoon = Super();
    gsm = Super(); 

    */
    telefoon = new Telefoon(vast,"vast");
    gsm = new Telefoon(mobiel, "mobiel");
    this.eMail = eMail;
}

//Methods.
public String toString() {
    return String.format("E-mail: %-15s %nTel: %-12s %nGSM: %-12s",eMail,telefoon.getNummer(), gsm.getNummer());
}

My problem is that The class 'ContactGegevens' extends Telefoon But in the constructor of ContactGegevens I still have to create 2 objects of class Telefoon rendering 'Extends Telefoon' useless. Can I do something like Telefoon telefoon = Super(//Param here);?

And also Why do I need a default constructor in Telefoon otherwise I get an error when instantiating the object 'Telefoon' in the constructor of 'ContactGegevens'.

Answer 1

As noted, the ContactGegevens class shouldn't inherit from Telefoon , because it does not satisfy the “is-a” logic of inheritance. Instead, it has multiple phone numbers.

But given the constraint you're operating with, I would suggest removing the telefoon member from ContactGegevens : it's replaced by the inheritance. This leaves us with:

public class ContactGegevens extends Telefoon {
    private String eMail;         //Email.
    private Telefoon gsm;         //Mobile phone number.

    public ContactGegevens(String vast, String mobiel, String eMail) {
        super("vast", vast);
        this.eMail = eMail;
        gsm = new Telefoon("mobiel", mobiel);
    }

    public String toString() {
        return String.format("E-mail: %-15s %nTel: %-12s %nGSM: %-12s", eMail, getNummer(), gsm.getNummer());
    }