Module 3: Abstraction & Encapsulation

Objective

The objective of this module is to get hands-on experience with the following topics:

1. Introduction to Abstraction
2. Abstract classes and interfaces
3. Access Modifiers (public, private, protected)

Lab 3.2

Objectives

1. Understand and implement packages in Java.
2. Understand the import statement.
3. Understand and implement access modifiers in Java.

Problem Statement

Copy the classes from the previous lab to the appropriate packages com.trainingmug.ecommerce.service and com.trainingmug.ecommerce.main

Tasks

1. Ensure that the necessary import statements are automatically generated by the IDE in Main.java, Payroll.java, and PayrollImpl.java.

   Example: Main.java

   package com.trainingmug.ecommerce.main;
   
   import com.trainingmug.ecommerce.Designer;
   import com.trainingmug.ecommerce.Developer;
   import com.trainingmug.ecommerce.Employee;
   import com.trainingmug.ecommerce.service.PayrollImpl;

   Hint: If you are unable to see them, expand the code at line 3.

2. In Employee.java make the following changes:

   • Make all instance variables and static variables private.
   • Make the no-argument constructor Employee() public.
   • Make all methods public.
   • Generate getter() and setter() methods for all instance and static variables.

3. In Developer.java make the following changes:

   • Make noOfProjects private.
   • Make all methods public.
   • Generate getter() and setter() methods for the noOfProjects property.
   • To remove errors when accessing properties directly, use getter methods.
     Example: empId -> getEmpId(), name -> getName().

4. In Designer.java make the following changes:

   • Make noOfWebsites private.
   • Make all methods public.
   • Generate getter() and setter() methods for the noOfWebsites property.
   • To remove errors when accessing properties directly, use getter methods.
     Example: empId -> getEmpId(), name -> getName().

5. In Main.java:

   • Remove the statements that access properties on employee1 and employee2 objects directly.
   • Hint: Make sure to save the files. All errors should now be resolved.

6. Run Main.java and observe that the output is the same as in the previous lab, but with properly implemented Object-Oriented Programming (OOP) principles.