Inheritance

Inheritance

1. Extendible

   • Use the extend keyword to extend a class
   • Parent class
     • Superclass
       • Being extend
   • Child class
     • Subclass
       • Add new methods and fields to influence the parent class
         • Method overriding
           • A new method from a subclass that has the same signature as a method in the parent class
         • Method overloading
           • A new method from a subclass that has the same name but different argument as a method in the parent class
       • Constructors
         • When creating a subclass object, its superclass is also instantiated
         • Keyword super
           • Represent an instance of the direct superclass of the current object
   • Is-a relationship
     • A subclass is a type of the superclass, but the superclass is not necessarily the subclass
   • Accessibility
     • A subclass can access its superclass's public and protected methods and fields

2. Inextensible

   • Use the final keyword or final classes to prevent classes from being subclassed