Java Programming: Lesson 34 - protected, final, and Abstract Classes смотреть онлайн

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In the previous video (https://youtu.be/UvG7Pn5GMPs), we began our discussion of abstraction. Here, we study abstract classes and polymorphism in greater detail.

The public keyword makes a variable OR METHOD available to any class
The private keyword makes a variable OR METHOD available only to that class
The protected keyword makes a variable OR METHOD available only to that class and any subclasses (or any subclasses of subclasses, ... ) It's like a "family" variable that's passed down to descendant classes

The final keyword makes the value of a variable constant, in a class or method constant. It can be instantiated (it doesn't have to be instantiated when it is first declared final), but it cannot be assigned a value more than once.

Abstract classes are classes that cannot be instantiated. They can have both concrete methods, which have formal definitions, and abstract methods, which have only headers and the word abstract in the method header and a semicolon at the end of the function definition. Abstract methods must be formally defined in any concrete classes that extend the abstract class.

0:35 Review of Abstract Classes
3:11 Review of protected Keyword
4:27 Review of final Keyword
5:32 NEW: Abstract Inheritance
10:16 NEW: Abstract Polymorphism
14:31 NEW: Multiple Concrete Subclasses of an Abstract Class

Ready for interfaces? Check the next lesson: https://youtu.be/dEDs5n2PXKo

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