How to extend a class with a different constructor?

Question

I am having difficulty extending a person class to a patient class

I have a Person class with a constructor looking like

  public Person(String firstname,String surname) {
        fFirstname=firstname;
        fSurname=surname;
    }

I then have a Patient Class

public class Patient extends Person

I want to have a constructor for a patient looking roughly like

public Patient(String hospNumber) {
    fFirstname = lookup(hospNumber,"firstname");
    fSurname = lookup(hospNumber,"surname");
}

However I get a complaint that the Patient constructor needs (String,String). I can see why this is, but can't see how to extend the person class for a patient.

Answer 1

Just pass the result of those two method calls to the super constructor:

public Patient(String hospNumber) {
    super(lookup(hospNumber,"firstname"), lookup(hospNumber,"surname"));
}

Those methods have to be static, since the this they would otherwise been called on hasn't been constructed yet when they're invoked.

Answer 2

Either you can have a default constructor in Person class

public Person() {

}

Or

You need to call constructor the Person class using super method as its a 2-arg constructor

public Patient(String hospNumber) {
    super(lookup(hospNumber,"firstname"), lookup(hospNumber,"firstname"));
}