Declaring object of subclass

Question

Im trying to create a instance of the subclass ''smycken'' but it does not seem to work as ''namn'' in the parameter gets an error.

public abstract class Värdesaker {

    String namn;
    double värde;
    double moms = 1.25;

    public static void main(String[] args) {

        Värdesaker v = new smycken(namn, false, 0);

    }

    class smycken extends Värdesaker {

        double vikt, ädelstenar;

        public smycken(String namn, boolean guld, int ädelstenar) {
            this.namn = namn;
            this.ädelstenar = ädelstenar;
            if (guld)
                this.värde = (2000 + (ädelstenar * 500)) * moms;
            else
                this.värde = (500 + (ädelstenar * 500)) * moms;

        }

First of all, you have to mark your class smycken as static so it can be used from the static main method. You are not creating a local variable in the main method. Which can be passed on as an argument to the constructor of your subclass. Namn variable is not accessible as its member variable of the class — Vikram Patil, May 01 '19 at 12:22
protected String namn; protected double värde; protected double moms; Also, call super() first from your child constructor. As the comment above states, the child cannot see the private variables of the father. — aran, May 01 '19 at 12:24
While it is really a *subclass*, the issue comes from being an *inner class*, perhaps *nested*. Then you can find countless topics: https://stackoverflow.com/questions/4070716/instantiating-inner-class and https://stackoverflow.com/questions/12690128/how-to-instantiate-non-static-inner-class-within-a-static-method being two of them. — tevemadar, May 01 '19 at 12:45

Vikram Patil · Accepted Answer · 2019-05-01T12:45:13.767

0

I have modified your code as follows. It seems to work. Following things are required

Changing access specifier to protected for member variables of super class Värdesaker ( Or you can provide getter-setters for access to private variables)
Mark smycken as static
The main method cannot access non-static, non-public member variables.So you have to instantiate your arguments or create as before using in constructor.

// modified class

  public abstract class Värdesaker {
  protected String namn;
  protected double värde;
  protected double moms = 1.25;

  public static void main(String[] args)
  {

    Värdesaker v = new smycken("Test", false, 0);

  }

  static class smycken extends Värdesaker
  {

    double vikt, ädelstenar;

    public smycken(String namn, boolean guld, int ädelstenar)
    {
      this.namn = namn;
      this.ädelstenar = ädelstenar;
      if (guld) {
        this.värde = (2000 + (ädelstenar * 500)) * moms;
      } else {
        this.värde = (500 + (ädelstenar * 500)) * moms;
      }

    }
  }
}

edited May 01 '19 at 12:45

answered May 01 '19 at 12:27

Vikram Patil

628
6
20

I have a doubt . It is an inner class right? It might already have access its enclosing members, why does we again extend it?? – Arasn May 01 '19 at 12:47
I think use case requested looks different https://www.geeksforgeeks.org/inner-class-java/ – Vikram Patil May 01 '19 at 12:57
it works now, thank you!! i also forgot to put ".." as it is a string hehe.. thank you all! – Roni Berri May 01 '19 at 13:53
@Roni, if you find answer useful could you please accept and upvote it? – Vikram Patil May 01 '19 at 14:08
@user3401493 absolutely!, i assume its the nike button to the left of the answer i should press – Roni Berri May 01 '19 at 14:17
Yes, I think you already accepted answer but upvote is remaining. – Vikram Patil May 02 '19 at 05:18

Declaring object of subclass

1 Answers1