How to get the reference class of an subclass object

I am getting into polymorphism but I can't seem to solve this issue. I can't seem to find the correct way of checking whether my object is referenced as the superclass or a subclass. Basically I want to utilize a method to do certain things, depending on the reference class, and NOT the object class. In this example I used "instanceof" in the if condition, but that is wrong of course since both will be listed as Animal...

Main class:

    public class Main {
    public static void main(String[] args) throws FileNotFoundException {
        Animal dog1 = new Dog();
        Dog dog2=new Dog();

        List<Animal> animalList = new ArrayList<>();
        animalList.add(dog1);
        animalList.add(dog2);

        for (Animal animal:animalList) {
            if (animal instanceof Animal){
                animal.talk();
            }
            else if(animal instanceof Dog){
                animal.talk();
                ((Dog)animal).walk();
            }
        }
    }
}

Animal class:

    public class Animal {
    public void talk(){
    System.out.println("Hello I'm an animal");
    }
  }

Dog class:

public class Dog extends Animal{
public void walk(){
    System.out.println("Dogs can walk");
  }
}

I would try something like this:

Animal animal1 = new Animal();
Animal animal2 = new Dog();

List<Animal> animalList = new ArrayList<>();
animalList.add(animal1);
animalList.add(animal2);

for (Animal animal : animalList) {
	animal.talk();
	if(animal instanceof Dog){
		((Dog)animal).walk();
	}
}

Not sure it can help.
In java you can define the same method with different parameters. Every reference to a dog object will be passed to the do(Dog dog) method. Every other animal to do(Animal animal)
But this is still based on the object type, not the reference. In your logic all references should be Animal as you are walking through a list of Animal.
Within the for loop there is no link to the dog1 variable anymore.

public class Main {
    public static void main(String[] args) throws FileNotFoundException {
        Animal dog1 = new Dog();
        Dog dog2=new Dog();

        List<Animal> animalList = new ArrayList<>();
        animalList.add(dog1);
        animalList.add(dog2);

        for (Animal animal:animalList) {
            do(animal);
        }
    }
    public static void do(Animal animal) {
        animal.talk();
    }
    public static void do(Dog dog) {
       dog.talk();
       dog.walk();
    }
}

If every Dog walks every time it talks, then Dog should become:

public class Dog extends Animal {
    @Override
    public void talk(){
        super.talk();
        walk();
    }

    public void walk() {
        System.out.println("Dogs can walk");
    }
}

and your main should then become like:

public class Main {
    public static void main(String[] args) {
        Animal dog1 = new Dog();
        Dog dog2 = new Dog();
        Animal plain = new Animal(); //Added a new plain Animal for testing.

        List<Animal> animalList = new ArrayList<>();
        animalList.add(dog1);
        animalList.add(dog2);
        animalList.add(plain);

        for (final Animal animal: animalList)
            animal.talk();
    }
}

As for your code, the problem is than every Animal reference points to either an Animal instance (or any class which extends it), or null. You could fix it by changing the order of the if conditions like so:

for (Animal animal: animalList) {
    if (animal instanceof Dog) {
        animal.talk();
        ((Dog)animal).walk();
    }
    else
        animal.talk();
}

which corresponds to:

for (Animal animal: animalList) {
    animal.talk();
    if (animal instanceof Dog)
        ((Dog)animal).walk();
}