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?