Abstract class or casting?

Question

I'm trying to figure out whether implementing individual methods of a subclass in an abstract superclass, or casting is the better way to go about the following scenario. Suppose I have an abstract class Animal which has two subclasses, Dog and Cat and a Main class where I save objects of Dog and Cat in an Animal array. The following is how I would go about using methods of the subclasses in a more generalized array.

class Main{
    public static void main(String[] args){
        Animal[] animalArray = new Animal[2];
        animalArray[0] = new Cat();
        animalArray[1] = new Dog();
        
        for (Animal a : animalArray){
            if (a.getClass().equals(Dog.class){
            ((Dog)a).bark();
            } else {
            ((Cat)a).meow();
            }
        }
    }
}

However a friend suggested that casting isn't best practice, and that I should define each method in the abstract superclass in the following way:

public abstract class Animal{

    public abstract String meow(){
        return null;
    }
    public abstract String bark();
        return null;
    }
}

After setting the return values of these methods to null I would need to use @Override and implement them in the respective subclasses.

Which way is better? I'm afraid the abstract class will be too large and will have methods assigned to subclasses that don't make sense (even if all they do is return null). I think by using casting I can make more precise uses of the methods.

Answer 1

meow() and bark() shouldn't be defined in the Animal class. These methods are specific to Cat and Dog classes. You should define an abstract method as shown below, in the Animal class and override it in the sub classes.

public abstract class Animal {
   public abstract String action() {};
}

public class Dog extends Animal {
   @Override
   public String action() {
       //your implementation (bark)
   }
}

public class Cat extends Animal {
   @Override
   public String action() {
      //your implementation (meow)
   }
}

Hope it answers your query.