Chapter 6

Chapter 6

1. INHERITANCE

   • Inheritance is what makes code extensible in any OOP language
   • The process of extending a class
     • extend a class by using the "extends" keyword in class declaration
     • extending a class is known as inheriting / subclassing
       • use the "final" keyword to prevent classes from being subclassed
       • extend a class by creating a new class
         • "new" keyword creates an instance of a subclass
           • keyword "super" represents an instance of the direct superclass of the current object
             • you can explicitly call the parents constructor from a subclass’s constructor with super keyword, super must be first statement in the constructor
             • super can call a hidden member or an overridden method in a superclass
           • "instanceof" keyword used to test if an object is of a specified type typically used in an if statement
       • subclass inherits all public methods and fields of its superclass
         • you can access a superclass public and protected methods and fields within the subclass, but you cannot access the private methods
       • method overriding - changing the behavior of a method in the parent class by writing in a subclass a method with the same signature as a method in the superclass
         • method overloading - only the name is the same but the list of arguments is not
     • “is-a” relationship is when you create a new class by inheritance
   • Gives you the opportunity to add functionality that does not exist in the original class
   • gives you the chance to change the behaviors of the existing class to better suit your needs