Inheritance

Inheritance

1. Makes code extensible in any OOP language

   • You can extend a class by creating a new class called the child or subclass
     • Gives the opportunity to add functionality that did not exist in the original class
     • A subclass can access its superclass's public and protected methods and fields

2. Extends keyword

   • This is normally the default setting for Java
   • Extended classes develop an "is-a" relationship

3. Overriding

   • Subclass can change the behavior of a method in the parent class
     • Occurs when the subclass method has the same signature as the parent class
   • Does not work for private methods
   • Cannot override a Final method

4. Calling Superclass constructors

   • A no-argument constructor is created in a subclass if one is not explicitly created
     • This ensures the first thing called in the subclass is the no- arg constructor of the direct superclass, using the keyword "Super"
       • You must explicitly call a parent class's constructor if there is no "no-arg" class in either class
       • super keyword can also call a hidden member or overridden method from the superclass

5. Type Casting

   • You can cast an object to another type
     • Can only cast from a subclass to its parent class

6. Final Keyword

   • Prevents a class from being extended further

7. Instanceof keyword

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