Question

Modify class GradeBook (Fig. 3.10 ) as follows: a) Include a second String instance variable that represents the name of the course's instructor. b) Provide a set method to change the instructor's name and a get method to retrieve it. c) Modify the constructor to specify two parameters - one for the course name and one for the instructor's name. d) Modify method displayMessage such that it first outputs the welcome message and course name, then outputs "This course is presented by:" followed by the instructor's name. Use your modified class in a test application that demonstrates the class's new capabilities.

Short answer

Added instructor's name to GradeBook, updated constructor, setters, getters, and displayMessage method, and tested the class.

Step-by-step solution

Add a Second String Instance Variable

Modify the `GradeBook` class to include a second `String` instance variable, `instructorName`. This will store the name of the instructor for the course. Add it inside the class before the constructor.

Create Set and Get Methods for Instructor Name

Create a `setInstructorName` method to allow changing the instructor's name, taking a String parameter and assigning it to the class's `instructorName` variable. Also, create a `getInstructorName` method that returns the current instructor's name stored in `instructorName`.

Modify Constructor for Two Parameters

Update the `GradeBook` constructor to accept two parameters: one for `courseName` and another for `instructorName`. Assign these parameters to the corresponding instance variables, initializing the class with both course and instructor names.

Update displayMessage Method

Modify the `displayMessage` method to first output the welcome message and course name. Then, add a line printing "This course is presented by: " followed by calling the `getInstructorName` method to display the instructor's name.

Test the Modified Class in a Test Application

Implement a test application by creating a new `GradeBook` object with a sample course name and instructor name. Call the `displayMessage` method on this object to demonstrate the new capabilities, showing both the course name and instructor name in the output.

Key concepts

Java programming

Java, known for its versatility, is a widely-used programming language that emphasizes object-oriented programming (OOP) principles. This makes it an excellent choice for developing complex software systems by enhancing understanding and reusability through its organized structure.
Java is platform-independent, meaning it can run on any device with the Java Virtual Machine (JVM). This feature appeals to developers since they can write code once and run it anywhere.
The language's robustness and security features make Java a preferred choice for both beginners and advanced programmers alike.

class modification

In object-oriented programming, modifying a class allows developers to adapt or enhance a program's functionalities. Making changes to a class means changing its structure, attributes, or methods. These modifications can improve the code's performance or add new features.
For example, modifying a class to include additional instance variables as requested in the exercise is a typical task. In the case of the `GradeBook` example, adding an instance variable for the instructor's name makes the class capable of storing more information.
Besides instance variables, a class can also be modified by updating its methods or constructors, to incorporate new functionalities using optimized and organized code.

instance variables

Instance variables play a crucial role in object-oriented programming by storing the data specific to each instance of a class. They are defined within a class but outside any method, constructor, or block. This means each object created from the class can have its version of the instance variables.
When you create a new object, instance variables are often initialized with values that are essential for the object’s functionality.
In the case of `GradeBook`, adding the `instructorName` as an instance variable allows each `GradeBook` object to store its own instructor's name, thus expanding its data handling capabilities. Utilizing get and set methods for these variables ensures controlled access and modification.

method creation

Creating methods is fundamental in Java programming and OOP, as methods define behaviors that a class's objects can perform. Methods can manipulate instance variables, enabling interaction with an object's state.
In our exercise, methods like `setInstructorName` and `getInstructorName` were introduced. These methods allow for setting and retrieving the instructor's name, encapsulating the instance variable's access and manipulation, ensuring data integrity.
For new features, the `displayMessage` method was modified to output both the course and instructor names. This showcases how methods can be crafted or enhanced to meet additional requirements and illustrate an object's operations.