Programming Polymorphism (OCR A Level Computer Science)

Programming Polymorphism

• To program polymorphism, you should already have a solid understanding of what polymorphism in Object Oriented Programming (OOP) is.

How do you Define Polymorphism?

Pseudocode 

1. Create a blueprint for a general animal:

• Define a template called Animal

• Give Animal a placeholder action called speak() that does nothing yet

2. Create a blueprint for a dog:

• Define a template called Dog based on the Animal template

• Override the speak() action for Dog to make it print "Woof"

3. Create a blueprint for a cat:

• Define a template called Cat based on the Animal template

• Override the speak() action for Cat to make it print "Meow"

4. Create a function to make animals speak:

• Define a function called make_sound(animal)

• Inside the function, tell the given animal to perform its speak() action

5. Create a dog and a cat:

• Build a Dog object and put it in a box labeled "dog"

• Build a Cat object and put it in a box labeled "cat"

6. Ask the dog and cat to speak:

• Call the make_sound() function with the dog object

• Call the make_sound() function with the cat object

Python

class Animal:
    def speak(self):
        pass

class Dog(Animal):
    def speak(self):
        print("Woof")

class Cat(Animal):
    def speak(self):
        print("Meow")

def make_sound(animal):
    # calling the speak method of the Animal class
    animal.speak()

dog = Dog()
cat = Cat()

make_sound(dog)
make_sound(cat)

Java

class Animal {
    public void speak() {
        // Empty default implementation
    }
}

class Dog extends Animal {
    @Override
    public void speak() {
        System.out.println("Woof");
    }
}

class Cat extends Animal {
    @Override
    public void speak() {
        System.out.println("Meow");
    }
}

public class Main {
    public static void makeSound(Animal animal) {
        animal.speak();
    }

    public static void main(String[] args) {
        Dog dog = new Dog();
        Cat cat = new Cat();

        makeSound(dog);
        makeSound(cat);
    }
}