Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code demonstrates the fundamental concepts of Object-Oriented Programming (OOP), specifically classes and objects.

1. Box Class:

   • The Box class acts as a blueprint for creating "box" objects.
   • It defines three instance variables (or fields): width, height, and depth, all of type double. These variables represent the dimensions of a box.
   • It has a constructor named Box(double w, double h, double d). A constructor is a special method that is called when you create a new object of the class. Its purpose is to initialize the object's state. This constructor takes three double values (w, h, d) as input and assigns them to the corresponding instance variables (width, height, depth) of the Box object being created.
   • It has a method named volume(). This method calculates and returns the volume of the box by multiplying its width, height, and depth.

2. BoxDemo6 Class:

   • This class contains the main method, which is the entry point of the Java program.
   • Object Creation:
     • Box mybox1 = new Box(10, 20, 30); This line creates a new Box object named mybox1. The new Box(...) part calls the Box constructor, passing 10, 20, and 30 as arguments. This initializes mybox1's width to 10, height to 20, and depth to 30.
     • Box mybox2 = new Box(40, 50, 60); Similarly, this line creates another Box object named mybox2 with dimensions 40, 50, and 60.
   • Variable Declaration:
     • double vol; A variable named vol of type double is declared to store the calculated volume.
   • Method Invocation and Output:
     • vol = mybox1.volume(); This line calls the volume() method on the mybox1 object. The mybox1 object's dimensions (10, 20, 30) are used for the calculation. The returned volume (10 * 20 * 30 = 6000.0) is stored in the vol variable.
     • System.out.println("Volume is " + vol); This line prints the calculated volume of mybox1 to the console.
     • vol = mybox2.volume(); This line calls the volume() method on the mybox2 object. The mybox2 object's dimensions (40, 50, 60) are used. The returned volume (40 * 50 * 60 = 120000.0) is stored in the vol variable, overwriting the previous value.
     • System.out.println("Volume is " + vol); This line prints the calculated volume of mybox2 to the console.

In essence, the code defines a reusable "template" for boxes and then uses that template to create specific box instances, each with its own dimensions, and then calculates and displays their volumes.

Algorithm

• Define a Class (Box):
  • Declare instance variables for width, height, and depth (type double).
  • Implement a constructor to initialize these instance variables with provided values.
  • Implement a method (volume) to calculate and return the product of width, height, and depth.
• Create a Main Program (BoxDemo6):
  • In the main method:
    • Create the first Box object (mybox1) using the constructor, providing initial dimensions.
    • Create the second Box object (mybox2) using the constructor, providing different initial dimensions.
    • Declare a variable (vol) to hold the volume.
    • Call the volume() method on mybox1 and store the result in vol.
    • Print the volume of mybox1.
    • Call the volume() method on mybox2 and store the result in vol (overwriting the previous value).
    • Print the volume of mybox2.