C# Chapter 9: Rectangle Class Quiz

Chapter 9: Using Classes and Objects - Practice Example

• Rectangle Class: A class representing a rectangle
• Fields:
  • length: Stores the rectangle's length.
  • width: Stores the rectangle's width.
• Methods:
  • SetLength(double len): Sets the rectangle's length.
  • SetWidth(double wid): Sets the rectangle's width.
  • GetLength(): Returns the rectangle's length.
  • GetWidth(): Returns the rectangle's width.
  • GetArea(): Returns the rectangle's area (length * width).

Writing the Code for the Class Fields

• Rectangle Class Definition:

  public class Rectangle
  {
      private double length;
      private double width;
  }
  

• Fields are declared as private
• double data type for length and width

Method Header for SetLength

• Access Specifier: public
• Return Type: void
• Method Name: SetLength
• Parameter: double len

Writing and Demonstrating the SetLength Method

• Method Body:

  public void SetLength(double len)
  {
      length = len;
  }
  

• Stores the value of len in the length field.

Method Header for GetLength

• Access Specifier: public
• Return Type: double
• Method Name: GetLength
• No Parameters

Writing and Demonstrating the GetLength Method

• Method Body:

  public double GetLength()
  {
      return length;
  }
  

• Returns the value stored in the length field.

Rectangle.cs (Version 1)

• Contains SetLength and SetWidth methods, with comments explaining their purposes and parameters
• private double length; and private double width; declare the instance fields for the rectangle's length and width

Rectangle.cs (cont'd)

• Contains GetLength, GetWidth, and GetArea methods, with comments explaining their purposes and return values
• Uses multiplication length * width to calculate and return the area.

RectangleDemo.cs

• RectangleDemo class containing Main method, demonstrating how to use a Rectangle object
• Rectangle box = new Rectangle(); creates a Rectangle object
• box.SetLength(10.0); Sets the length of the box
• box.SetWidth(20.0); Sets the width of the box
• Outputs the length, width, and area of the box using Console.WriteLine()

Create a Rectangle object

• Rectangle box = new Rectangle(); creates a Rectangle object
• The variable 'box' holds the address of the Rectangle object.

Calling the SetLength Method

• box.SetLength(10.0); sets the length of 'box'
• 'box' variable now holds the address of rectangle object with length = 10, width = 0

Accessors and Mutators of Rectangle Class

• Setters (Mutators):
  • Modify object data
  • e.g., SetLength, SetWidth
• Getters (Accessors):
  • Access object data
  • e.g., GetLength, GetWidth, GetArea

Rectangle.cs (Version 2)

• Includes parameterised constructor Rectangle(double len, double wid)
• Parameterless constructor Rectangle()
• Sets default values for length and width if no parameters are given

Rectangle.cs (cont'd)

• Contains SetLength, SetWidth, GetLength, GetWidth, and GetArea methods, with detailed comments

Instance Fields and Methods

• Instance fields and methods require an object to be created to be used.
• Each object can have different values for its fields.

RoomArea.cs

• Creates 3 Rectangle objects (kitchen, bedroom, den) to hold area.
• Prompts user for dimensions of each room
• Calculates total area of the rooms.
• Outputs the total area of the rooms

RoomArea.cs (cont'd)

• Contains code to get and store room dimensions using user input.
• Implements calculations for total area.
• Prints the total area to the console

States of Three Different Rectangle Objects

• Shows the state (length, width) of each of the three Rectangle objects created in the RoomArea class, after dimensions are entered.

Rectangle.cs (Version 3)

• Introduces properties for Length and Width to encapsulate the fields.
• Methods use properties, instead of directly accessing the length and width fields.

Rectangle.cs (cont'd)

• Includes methods that use the properties Length and Width to get and set the values (getters & setters).

PropertyTest.cs

• Demonstrates the use of Rectangle class properties.
• Sets length and width of a Rectangle object, calculates and displays the area of the object.