In object oriented world, inheritance is most common feature in which sub class or derived class can take advantage to accessing base class functionality or an existing class can be further extended to create new one using inheritance.
In this example,
extend keyword is used to create subclass which is classB. The
classB has base class called
classA. Here, class
classB is deriving from
classA and gaining access to its features.
In the example, we instantiated sub class and created object by passing parameters value. This will call subclass constructor, which will call further base class constructor and set the value to the member of base class. Next, call print function of base class from sub class which will print the value.