Ch 6: Inheritance

Ch 6: Inheritance

1. The process of extending a class in OOP

2. The 'extends' Keyword

   • used to extend a class in the class declaration, after class name but before parent class

3. The 'is-a' Relationship

   • Special relationship that is formed between the subclass and superclass when you create a new class with inheritance
     • subclass is special type of superclass
     • subclass inherits all public methods and fields of its superclass
       • Accessibility
         • can access superclass's public and protected methods & fields, but not private methods

4. Method Overriding

   • changing the behavior of a method in the parent class
     • done by writing a method in the subclass that has the same signature as a method in the parent class
       • can override superclass's public & protected methods; cannot override final methods
       • 'method overloading' refers to creating a method with the same name but different list of arguments

5. Calling Superclass's Constructors

   • When creating a child object, all its parent classes are also instantiated
     • the keyword 'super' represents an instance of the direct superclass of the current object

6. Calling the Superclass's Hidden Members

   • 'super' keyword can be used to call a hidden member or an overridden method in superclass
     • can access any member in the superclass that is visible to subclass

7. Type Casting

   • can only cast an instance of a subclass to its parent class
     • Upcasting
     • assign object of type subclass to a reference variable of type superclass

8. Final Classes

   • by using keyword 'final' in class declaration, you can prevent others from extending your class

9. 'instanceOf' Keyword

   • can be used to test if an object is of a specified type