In my quest to correctly grasp Interface best practices, I have noticed declarations such as:

```
List<String> myList = new ArrayList<String>();

```

instead of 

```
ArrayList<String> myList = new ArrayList<String>();

```

-To my understanding the reason is because it allows flexibility in case one day you do not want to implement an ArrayList but maybe another type of list.

With this logic, I set up an example:

```
public class InterfaceTest {

    public static void main(String[] args) {

        PetInterface p = new Cat();
        p.talk();

    }

}

interface PetInterface {                

    public void talk();

}

class Dog implements PetInterface {

    @Override
    public void talk() {
        System.out.println("Bark!");
    }

}

class Cat implements PetInterface {

    @Override
    public void talk() {
        System.out.println("Meow!");
    }

    public void batheSelf() {
        System.out.println("Cat bathing");
    }

}

```

My question is, I cannot access the batheSelf() method because it only exists for Cat. That leads me to believe that I should only declare from an Interface if I am only going to use methods declared in the Interface (and not extra methods from the subclass), otherwise I should declare from the Class directly (in this case Cat). Am I correct in this assumption?