Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code defines two classes: Box and BoxDemo5.

1. Box Class:

   • This class serves as a blueprint for creating "Box" objects. It has three instance variables: width, height, and depth, all of type double to store the dimensions of a box.
   • It includes a default constructor named Box(). When a new Box object is created without specifying any parameters, this constructor is automatically called. Inside this constructor, it first prints "Constructing Box" to the console, and then it initializes the width to 10, height to 20, and depth to 30. This means every Box object created using this default constructor will initially have these fixed dimensions.
   • It also has an instance method called volume(). This method calculates the volume of the box by multiplying its width, height, and depth instance variables and returns the result as a double.

2. BoxDemo5 Class:

   • This class contains the main method, which is the entry point for the Java application.
   • Inside the main method, the line Box mybox1 = new Box(); creates a new object (an instance) of the Box class. When new Box() is executed, the Box() constructor is invoked, printing "Constructing Box" and setting mybox1's dimensions to 10, 20, and 30.
   • Next, double vol = mybox1.volume(); calls the volume() method on the mybox1 object. This method calculates 10 * 20 * 30, which is 6000.0, and this value is stored in the vol variable.
   • Finally, System.out.println("Volume is " + vol); prints the string "Volume is " followed by the calculated volume (6000.0) to the console.

In essence, the program defines what a "Box" is, how to create one with default dimensions, and how to calculate its volume. Then, it demonstrates creating a specific "Box" object and finding its volume.

Algorithm

1. Define a class named Box to represent a three-dimensional box.
2. Declare three instance variables (width, height, depth) of type double within the Box class to store the dimensions.
3. Implement a default constructor Box() within the Box class:
   • Print a message indicating that a Box is being constructed.
   • Initialize width to 10, height to 20, and depth to 30.
4. Implement an instance method volume() within the Box class:
   • Calculate the product of width, height, and depth.
   • Return the calculated volume as a double.
5. Define a class named BoxDemo5 which will contain the main method.
6. Inside the main method:
   • Create an object (instance) of the Box class using the default constructor, storing it in a variable named mybox1.
   • Call the volume() method on the mybox1 object.
   • Store the returned volume in a double variable named vol.
   • Print a message to the console displaying the calculated volume.