Java: OOP Basics

What you will learn

Inheritance extends a class, polymorphism lets you treat subclasses as their parent type, and annotations like @Override.

public class Animal {
    public void speak() {
        System.out.println("...");
    }
}

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

extends creates an is-a relationship: a Dog is an Animal. The subclass inherits all non-private members.

Polymorphism

Animal myPet = new Dog();
myPet.speak();  // "Woof!" -- the Dog version runs

The JVM decides at runtime which method to call (dynamic dispatch).

Quick check below!