My output comes out Null instead of using the default value for strings

Question

I have a string that is being set to a default when the input is outside of the specified values but it keeps returning null instead of the default value. what code am I missing to have the correct output?

I find that my integer and double values use the default correctly but my strings don't.

//This is a clip from my front end

import java.util.Scanner;
public class AnimalFrontEnd {
    public static final int ARRAY_SIZE = 10;
    Scanner keyboard = new Scanner(System.in) ;

    public static void main(String[] args) {
        boolean cont = true;
        int input = 0;
        int type = 0;
        AnimalCollection collection = new AnimalCollection(ARRAY_SIZE);
        Scanner keyboard = new Scanner(System.in) ;
        String rName = "";
        System.out.println("Welcome to the Cat and Dog Collection");
        while(cont) {
            System.out.println("1. Add a cat or dog \n2. Remove a cat or dog \n3. Quit \nEnter a selection");
            input = Integer.parseInt(keyboard.nextLine());
            switch(input) {
            case 1:
                System.out.println("Would you like to add \n1. A House Cat \n2. A Leopard \n3. A Domestic Dog \n4. A Wolf");
                type = Integer.parseInt(keyboard.nextLine());
                switch(type) {
                case 1:
                    HouseCat kitty = getHCat();
                    collection.addAnimal(kitty);
                    break;

//Further down in my front end

private static HouseCat getHCat() {
        String name;
        double weight;
        String mood;
        String cType;

        Scanner keyboard = new Scanner(System.in) ;
        System.out.println("Enter the cat's name, weight, mood, and type");
        name = keyboard.nextLine();
        weight = Double.parseDouble(keyboard.nextLine());
        mood = keyboard.nextLine();
        cType = keyboard.nextLine();
        return new HouseCat(name, weight, mood, cType);
    }

//my abstract class

public abstract class Animal {
    public String name;
    public double weight;

    Animal(){
        this.name = "Cuddles";
        this.weight = 0;
    }
    public Animal(String name, double weight) {
        this.setName(name);
        if(weight>0) {
            this.setWeight(weight);
        }
        else {
            System.out.println("Invalid weight");
        }
    }
    public String getAName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setWeight(double weight) {
        this.weight = weight;
    }
    public String toString() {
        return "Name: "+name+" Weight: "+weight;
    }
}

//an extension of animal

public class Cat extends Animal {
    public String mood;

    Cat(){
        this.mood = "Sleepy";
    }
    public Cat(String name, double weight, String mood) {
        super(name, weight);
        if(mood.equalsIgnoreCase("sleepy")||mood.equalsIgnoreCase("playful")||mood.equalsIgnoreCase("hungry")) {
            this.setMood(mood);
        }
        else {
            System.out.println("Invalid mood");
        }
    }
    public String getMood() {
        return mood;
    }
    public void setMood(String mood) {
        this.mood = mood;
    }
    public String toString() {
        return super.toString()+" Mood: "+mood;
    }
}

//the class that extends from Cat

public class HouseCat extends Cat {
    public String cType;

    HouseCat(){
        this.cType = "Short Hair";
    }
    public HouseCat(String name, double weight, String mood, String cType) {
        super(name, weight, mood);
        if(cType.equalsIgnoreCase("Short Hair")||cType.equalsIgnoreCase("Bombay")||cType.equalsIgnoreCase("Ragdoll")||cType.equalsIgnoreCase("Sphinx")||cType.equalsIgnoreCase("Scottish Fold")) {
            this.setCType(cType);
        }
        else {
            System.out.println("Invalid type");
        }
    }
    public String getCType(){
        return cType;
    }
    public void setCType(String cType) {
        this.cType = cType;
    }
    public String toString() {
        return super.toString()+" Type: "+cType;
    }
}

That I expect to show up:

Welcome to the Cat and Dog Collection
1. Add a cat or dog 
2. Remove a cat or dog 
3. Quit 
Enter a selection
1
Would you like to add 
1. A House Cat 
2. A Leopard 
3. A Domestic Dog 
4. A Wolf
1
Enter the cat's name, weight, mood, and type
Booph
23
unhappy
maine coon
Invalid mood
Invalid type
Collection: Name: Booph Weight: 23.0 Mood: Sleepy Type: Short Hair

What actually shows up:

Welcome to the Cat and Dog Collection
1. Add a cat or dog 
2. Remove a cat or dog 
3. Quit 
Enter a selection
1
Would you like to add 
1. A House Cat 
2. A Leopard 
3. A Domestic Dog 
4. A Wolf
1
Enter the cat's name, weight, mood, and type
Booph
23
unhappy
maine coon
Invalid mood
Invalid type
Collection: Name: Booph Weight: 23.0 Mood: null Type: null

score 2 · Accepted Answer · answered Apr 05 '19 at 06:47

Your house cat has two constructors:

// one constructor
HouseCat(){
    this.cType = "Short Hair";
}

// another constructor
public HouseCat(String name, double weight, String mood, String cType) {
    super(name, weight, mood);
    if(cType.equalsIgnoreCase("Short Hair")||cType.equalsIgnoreCase("Bombay")||cType.equalsIgnoreCase("Ragdoll")||cType.equalsIgnoreCase("Sphinx")||cType.equalsIgnoreCase("Scottish Fold")) {
        this.setCType(cType);
    }
    else {
        System.out.println("Invalid type");
    }
}

You are calling the constructor with 4 parameters in your front end, not the parameterless constructor, so this.cType = "Short Hair"; never got run.

The same thing happens in Cat - you are calling the constructor with 3 parameters, not the parameterless one that sets mood to a default value.

To fix this, just remove the parameterless constructors and instead initialise the variables inline:

// in HouseCat
public String cType = "Short Hair"; // btw you shouldn't use public fields.

// in Cat
public String mood = "Sleepy";

score 0 · Answer 2 · answered Apr 05 '19 at 06:47

When you create Object of HouseCat you called parameterized Constructor and in your default constructor you initialized Type and Mood Thats why these are null.

you need to set these values in your parameterized Constructor then they will show your expecyted output. Like Housecat constructor sholud be modify

public HouseCat(String name, double weight, String mood, String cType) {
        super(name, weight, mood);
        if(cType.equalsIgnoreCase("Short Hair")||cType.equalsIgnoreCase("Bombay")||cType.equalsIgnoreCase("Ragdoll")||cType.equalsIgnoreCase("Sphinx")||cType.equalsIgnoreCase("Scottish Fold")) {
            this.setCType(cType);
        }
        else {
            System.out.println("Invalid type");
            this.cType = "Short Hair";//<------------- set default value here
        }
    }

and Cat Constructor should be modify like

public Cat(String name, double weight, String mood) {
        super(name, weight);
        if(mood.equalsIgnoreCase("sleepy")||mood.equalsIgnoreCase("playful")||mood.equalsIgnoreCase("hungry")) {
            this.setMood(mood);
        }
        else {
            System.out.println("Invalid mood");
           this.mood = "Sleepy";//<-------------  set default value here
        }
    }

score 0 · Answer 3 · answered Apr 05 '19 at 06:54

you have created two constructors in your Cat class :

Cat(){
        this.mood = "Sleepy";
    }

and

    public Cat(String name, double weight, String mood) {
        super(name, weight);
        if(mood.equalsIgnoreCase("sleepy")||mood.equalsIgnoreCase("playful")||mood.equalsIgnoreCase("hungry")) {
           this.setMood(mood);
        }
        else {
            System.out.println("Invalid mood");
        }
    }

Only the first one (with no param) initializes the mood field. And you obviously use the other one to create your instance...

You have multiple solutions there : 1. remove the unused constructor and initilize mood in the other constructor 2. change the unused constructor into a 'simple' method that you will call right after super in your constructor 3. ...

Example :

public Cat(String name, double weight, String mood) {
  super(name, weight);
  this.mood = "Sleepy";

 if(mood.equalsIgnoreCase("sleepy")||mood.equalsIgnoreCase("playful")||mood.equalsIgnoreCase("hungry")) {
            this.setMood(mood);
        }
        else {
            System.out.println("Invalid mood");
        }
    }

HTH!

My output comes out Null instead of using the default value for strings

3 Answers3