Inheritance

Inheritance

1. Definition

   • The process of extending a class
     • All classes extend the java.lang.Object class

2. Performed using the "extends" keyword

   • Ex: public class Child extends Parent

3. Uses

   • extending traits from the superclass to various subclasses
     • Ex: All animals might eat, but only some have fins
       • So you would extend "eat" from Animal into Fish and Bird
   • Subclasses can access the superclass' public methods and fields
     • Method Overriding
       • Changing methods from the parent class using the child class
   • Calling a parent class' constructor methods
     • Done implicitly all the way up the chain
     • Can be done explicitly through "super"
   • Type Casting
     • Upcasting: changing the type of a variable to its parent class
     • Downcasting: changing the type to its subclass
       • Only if upcasting was already used for that variable

4. Prevention

   • Calling something "final" will prevent it from being extended
   • "instanceOf" can tell you what datatype an object is
     • Will return true or false