Pet.java

// ============================================
// Abstraction Example ~ Pet Sound System
// Author ~ Vikas Kumar
// Topic ~ OOP ~ Abstraction ~ Inheritance
// ============================================

// Abstract class ~ Cannot be instantiated
abstract class Animals {
    // Abstract method ~ Must be implemented by child
    abstract void sound();
}

// Child class 1 ~ Dog implements sound
class Dog extends Animals {
    @Override
    public void sound() {
        System.out.println("Woof");
    }
}

// Child class 2 ~ Cat implements sound
class Cat extends Animals {
    @Override
    public void sound() {
        System.out.println("Meow");
    }
}

// Main class ~ Program entry point
class Pet {
    public static void main(String[] args) {

        // Polymorphism style ~ Parent reference
        Animals a1 = new Dog();
        Animals a2 = new Cat();

        // Calling overridden methods
        a1.sound(); // Dog sound
        a2.sound(); // Cat sound
    }
}