Inheritance in Java

Explanation

This Java code demonstrates a fundamental concept in Object-Oriented Programming (OOP) called inheritance. It defines two classes: employee and department.

1. employee Class:

   • This class serves as the base class or superclass.
   • It represents a generic employee with two private attributes: eno (employee number, an integer) and ename (employee name, a string). Being private, these attributes can only be accessed directly from within the employee class itself, enforcing encapsulation.
   • It provides two public methods:
     • setemp(int no, String name): This method is used to set the employee number and name.
     • putemp(): This method is used to display the employee number and name to the console.

2. department Class:

   • This class is the derived class or subclass. The extends employee keyword signifies that department inherits from employee. This means a department object automatically gains all the public and protected members (attributes and methods) of the employee class.
   • In addition to the inherited members, department has its own specific private attributes: dno (department number, an integer) and dname (department name, a string).
   • It also provides its own public methods:
     • setdept(int no, String name): This method sets the department number and name.
     • putdept(): This method displays the department number and name.
   • The main method is located within the department class, making it the entry point for execution.
     • Inside main, an object d of the department class is created.
     • d.setemp(22,"Nathan");: Here, the department object d calls the setemp() method. This method was inherited from the employee class. It sets the employee number to 22 and the employee name to "Nathan" for this specific department object.
     • d.setdept(1,"Programming");: The department object d then calls its own setdept() method to set its department number to 1 and department name to "Programming".
     • d.putemp();: The department object d calls the inherited putemp() method to display the employee details (Nathan, Empno 22).
     • d.putdept();: Finally, the department object d calls its own putdept() method to display the department details (Programming, Deptno 1).

In essence, the department object d now holds both employee-specific information (inherited) and department-specific information (its own), and can perform operations related to both, showcasing how inheritance allows a subclass to extend and specialize the functionality of a superclass.

Algorithm

1. Define a base class employee with private attributes for employee number (eno) and name (ename).
2. Implement public methods setemp() to initialize these attributes and putemp() to display them.
3. Define a derived class department that extends the employee class, thereby inheriting its attributes and methods.
4. Add private attributes specific to the department class: dno (department number) and dname (department name).
5. Implement public methods setdept() to initialize these department-specific attributes and putdept() to display them.
6. In the main method:
   • Create an instance of the department class.
   • Call the inherited setemp() method on the department object to set employee details.
   • Call the department's own setdept() method on the same object to set department details.
   • Call the inherited putemp() method on the department object to display employee details.
   • Call the department's own putdept() method on the same object to display department details.