Inheritance

Inheritance

1. Benefits of inheritance

   • Gives you the opportunity to add functionalities not available in the parent class
   • Gives you the chance to alter the behavior of the existing class to better suit your specific needs

2. extends: Keyword used to extend a class

   • ex. public class Parent {} public class Child extends Parent {}

3. Is-a relationship: A relationship between subclasses and a superclass where the subclass "is a" special type of the super class. This relationship does not hold true in the other way

   • e.g. A cat, a dog, and a cow are all animals, but an animal is not necessarily a cat, dog, or cow

4. Accessibility

   • Public, protected, and default methods and fields of a superclass are accessible from a subclass. On the other hand, private methods and fields are not accessible

5. Overriding: changing the behavior of a method from the superclass in the subclass

   • Overriding a method is done by writing the same method signature from the superclass and then either altering the arguments entered as parameters or changing the code within the method

6. Calling a superclass's constructor

   • Whenever you create an object of a subclass, the java compiler implicitly instantiates all the superclasses of the specified subclass
   • super: keyword used to explicitly call the constructor of the direct superclass of a subclass. in addition it can be used to access hidden members and overridden methods of the superclass

7. Type Casting: Casting an object of one type to another type

   • Downcasting: Casting an object of a superclass to an object of a subclass
   • Upcasting: Casting an object of a subclass to an object of a superclass

8. Final: keyword used to prevent a class from being extended

9. instanceof: keyword used to test if an object is of a specified type