When we call a method that contains parameters, the arguments we place in our method call must match the parameter type. Similar to the previous exercise, polymorphism gives us a little more flexibility with the arguments we can use.

If we use a superclass reference as a method parameter, we can call the method using subclass reference arguments!

For example, imagine the class ScaryStory, whose constructor takes in a reference to the Monster class:

class ScaryStory {
  Monster monster;
  String setting;

  public ScaryStory(Monster antagonist, String place) {
    monster = antagonist;
    setting = place;
  }

  public void tellStory(){
    System.out.println("Once upon a time, " + monster.name + " was at " + setting + " looking to scare some mortals.");
  }

  public static void main(String[] args) {
    Monster dracula;
    dracula = new Vampire("Dracula");
    ScaryStory countDracula = new ScaryStory(dracula, "Dracula Castle");
    countDracula.tellStory();
  }
}

In the main() method, we used a reference of the class Vampire as our argument even though the constructor requested an object of class Monster. This is allowed because Vampire is a subclass of the Monster class.