Clarification in reference variable downcasting in java

Question

Below is the sample code

class Animal {
    void makeNoise() {System.out.println("generic noise"); }
}

class Dog extends Animal {
    void makeNoise() {System.out.println("bark"); }
    void playDead() { System.out.println("roll over"); }
}

class DogTest {
    public static void main(String [] args) {
        Animal animal = new Animal();
        Dog d = (Dog) animal; 
        d.makeNoise();
    }
}

Above code compiles well but when i try to run it, i get

java.lang.ClassCastException

My assumption is it should print "generic noise" because at run time it should invoke actual Animal object makeNoise() method without giving any exception.

Answer 1

You can't cast an arbitrary Animal instance to a Dog instance, unless the instance you are casting is actually a Dog or a sub-class of Dog.

It would make more sense for the Animal class to be abstract, since an actual Animal that can be instantiated should be a specific Animal, such as Dog, Cat, etc...