Subclasses

Method to create hierarchy between classes by inheriting from other classes
parent and child classes
extends extend a class to show its inherited and extends functionality
Subclass inherits all methods and fields from superclass, and constructor can be carried out from subclass
super refers to superclass or parent objects

// Hacks 1
private class Plane {
    private String model = "Boeing 737";
    private int age = 3; //two attributes

    public void getAge(String model, int age) {
        println("Age: " + age);
    }
}

private class Jet extends Plane {
    private String color = "blue";
    
}

Overload & Override

Overload happens when there are two methods with same name but different arguments or parameters
Method override happens when child class has the same method that is present in a parent class, overwrites base class method

//hack 2
public class Plane {
    private String model = "Boeing 737";
    private int age = 3;

    public void engineBurr() {
        System.out.println("brrrrrr");
    }
}

private class Jettison extends Plane {
    public Jettison(String model, int age, String color) {
        super(model, age); 
        this.color = color; 

        @Override
        public void engineBurr() {
        System.out.println("BRRRRRRRRR"); 
    }

}

Polymorphism

Ability of class to provide different implementations of methods, such as overloading, overriding, late binding

//Hack 3
private class Jets extends Plane {
    @Override
    public void getAge(String model, int age, String color) {
        println("Age: " + age);
    }

    public void getAge(int age, String color) {
        println("Age: " + age);
    }
}