Question

Developing a set of classes demonstrating inheritance - in class work

Answer 1

Inheritance :- The process by which one class acquires the properties(data members)and functionalities(methods) of another class is called inheritance. The aim of inheritance is to provide the reusability of code so that a class has to write only the unique features and rest of the common properties and functionalities can be extended from the another class.

Child Class: The class that extends the features of another class is known as child class, sub class or derived class.

Parent Class: The class whose properties and functionalities are used(inherited) by another class is known as parent class, super class or Base class.

Inheritance Example

In this program, we have a base class Teacher and a sub class PhysicsTeacher. Since class PhysicsTeacher extends the designation and college properties and work() method from base class, this way the child classes like MathTeacher, MusicTeacher and PhysicsTeacher do not need to write this code and can be used directly from base class.

class Teacher {
   String designation = "Teacher";
   String collegeName = "Beginnersbook";
   void does(){
        System.out.println("Teaching");
   }
}

public class PhysicsTeacher extends Teacher{
   String mainSubject = "Physics";
   public static void main(String args[]){
        PhysicsTeacher obj = new PhysicsTeacher();
        System.out.println(obj.collegeName);
        System.out.println(obj.designation);
        System.out.println(obj.mainSubject);
        obj.does();
   }
}

Output:

Beginnersbook
Teacher
Physics
Teaching

The important point to note in the above example is that the child class is able to access the private members of parent class through protected methods of parent class. When we make a instance variable(data member) or method protected, this means that they are accessible only in the class itself and in child class. These public, protected, private etc. are all access specifiers