Class returning the extended class' parameter instead of it's own parameter when using an-CodePudding

Sorry if the title is a little bit confusing! I got this class called Flower that extends a Plant class (for a school assignment) and I have a getType() method in Plant which just returns this.type . My issue is that when I run this method on a Flower object, instead of returning the type of Flower, it just returns null (which is the default return in the Plant class). I was wondering if there is any way to fix this without having to override the method, because that would kind of defeat the whole point of the assignment. The code I have is as below:

Plant Class:

public class Plant {
    
    protected List<String> plot = new ArrayList<>();
    private String type;
    
    public Plant() {
        //Some stuff here

        this.type = null;
    }
    
    public String getType() {
        return this.type;
    }
    //More stuff for the class here

Flower Class:

public class Flower extends Plant {
    private String type;
    private int size;

    public Flower(String type) {
        this.plot = new ArrayList<>();
        this.type = type;
        this.size = 0;

        //More code not important for the question goes here...

Thank you for your help in advance!

CodePudding user response：

You need to remove the private String type; from the Flower class.

What is happening is your child class (Flower) declares a String 'type' and it is hiding the Plant's 'type' field.

Think of it like this - a child can see a parents fields, but a parent can't see a child's fields.

So, when you set type in Flower it is not available for Plant - if you do not declare type in Flower, when you set it in Flower it will be visible to Plant, since that's where it's declared.

CodePudding user response：

The problem you are facing is, that your Plant class and your Flower class each have their own type. And since you don't override the getType() method in your Flower class the return value will always be the type of Plant which is null.

You have some options to solve that problem. Either you do the same thing you did with plot where you make the field protected and assign it in the constructor of Flower.

public class Plant {
    protected List<String> plot;
    protected String type;

    public Plant() {
        this.plot = new ArrayList<>();
    }

    public String getType() {
        return this.type;
    }
}

public class Flower extends Plant {
    private int size;

    public Flower(String type) {
        this.type = type;
        this.size = 0;
    }
}

Or since every Plant has a type you could use the "cleaner" version, where you use super to let Plant handle the assignment.

public class Plant {
    protected String type;
    protected List<String> plot;

    public Plant(String type) {
        this.type = type;
        this.plot = new ArrayList<>();
    }

    public String getType() {
        return this.type;
    }
}

public class Flower extends Plant {
    private int size;

    public Flower(String type) {
        super(type);
        this.size = 0;
    }
}