How to add properties to ArrayLists that include inheritance?

Question

I'm doing an assignment on inheritance and I have so far created a superclass a subclass. Within these classes, there are methods that have been added to define information such as an animal's name or age. Now I have been asked to do the following:

Create a Demo class with a main method that creates an ArrayList of Animal objects. Fill the list with different animals, also with different names and ages.

I'm completely confused by this. If I try to create animals within my new ArrayList it tells me that the Animal class is abstract and cannot be instantiated. Here is the contents of the relevant classes:

Animal class (super class)

abstract public class Animal 
{

    int age;
    String name;
    String noise;

Animal(String name, int age)   
{
    this.age = age;
    this.name = name;
} 

Animal()
{

  this("newborn", 0);
}

abstract public void makeNoise();

public String getName() {
        return name;
    }
  public int getAge()
    {
        return age;
    }

    public void setName(String newName) {
        name = newName;
    }

abstract public Food eat(Food x) throws Exception;

abstract public void eat(Food food, int count) throws Exception;


}

Wolf class (sub class)

import java.util.ArrayList;

public class Wolf extends Carnivore
{

            ArrayList<Food> foodGroup = new ArrayList<>();
String name;
int age;

Wolf(String name, int age)   
{  
    this.name = name;
    this.age = age;
}
Wolf()
{
  super();
}
    public void makeNoise()  
    {
        noise = "Woof!";
    }
    public String getNoise()  
    {
        return noise;
    }

    public Food eat(Food x) throws Exception
    { 
        if (x instanceof Meat) {
                return x;
            } else {
               throw new Exception("Carnivores only eat meat!");
            }
    }
public void eat(Food food, int count) {
    while (count > 0) {
        addFood(food);
        count--;
    }
}


public void addFood(Food inFood)
{
  foodGroup.add(inFood);
}
}

Demo class

import java.util.ArrayList;

public class Demo {

    public static void main(String[] args) 
    {
                    ArrayList<Animal> animalGroup = new ArrayList<>();
     //Add new Animals with properties such as name and age?           
     Animal wolf1 = new Wolf();

    addAnimal(new Wolf("lnb1g16", 6));

    }

    public static void addAnimal(Animal inAnimal)
{
    animalGroup.add(inAnimal);
}

}

Apparently I'm suppose to create an array of Animals in the Demo class based off of these prior classes? I don't understand how this would be done and why I need to create a another main method either. Any help on how I would write the Demo class would be much appreciated as I'm confused by what I have been asked to do, thanks.

Does Carnivore extend Animal? If so try to create a wolf and add it to your ArrayList - does it work? If not what is the error? — Scary Wombat
Carnivore does extend Animal. When I create a new wolf object and then try to add it to the ArrayList like this wolf1(new Animal("Wolf", 6)); I get the error "Animal is abstract, cannot be instantiated". — Ben

Sam Sam · Accepted Answer · 2016-11-28T01:43:44

Demo class

public static void main(String[] args) 
{
                ArrayList<Animal> animalGroup = new ArrayList<>();
 //Add new Animals with properties such as name and age?           
 Animal wolf1 = new Wolf();

animalGroup.add(new Wolf("sam", 5));
animalGroup.add(new Wolf("george", 5));
animalGroup.add(new Wolf("patrick", 7));

}

How to add properties to ArrayLists that include inheritance?

1 Answers