Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code demonstrates the fundamental concepts of Object-Oriented Programming (OOP) in Java, specifically focusing on classes, objects, and methods with parameters.

Let's break it down step-by-step:

1. class Box: This line declares a blueprint for creating "Box" objects. Think of it like a cookie cutter. It defines what properties (data) a Box will have and what actions (methods) it can perform.

   • double width; double height; double depth;: These are the instance variables or attributes of the Box class. Every Box object created from this blueprint will have its own width, height, and depth.
   • double volume(): This is a method named volume. It's an action that a Box object can perform. This method calculates and returns the volume of the box using its width, height, and depth.
   • void setDim(double w, double h, double d): This is another method named setDim. The void keyword means this method doesn't return any value. This method is designed to set or initialize the dimensions (width, height, depth) of a Box object. It takes three parameters: w (for width), h (for height), and d (for depth), which are of type double. Inside the method, it assigns the values passed as arguments to the object's corresponding instance variables.

2. class BoxDemo4: This is another class that contains the main method, which is the entry point for executing a Java program.

   • public static void main(String args[]): This is the standard main method signature.
   • Box mybox1 = new Box();: This line creates an object named mybox1 from the Box class. new Box() is the constructor call that allocates memory for a new Box object and initializes its instance variables (which will be 0.0 for doubles by default). mybox1 is an instance of the Box class.
   • Box mybox2 = new Box();: Similarly, this line creates another independent Box object named mybox2.
   • double vol;: This declares a variable named vol of type double to store the calculated volume.
   • mybox1.setDim(5, 10, 15);: This line calls the setDim method on the mybox1 object. The values 5, 10, and 15 are passed as arguments to the w, h, and d parameters respectively. This sets the width of mybox1 to 5, height to 10, and depth to 15.
   • mybox2.setDim(2, 4, 6);: This line does the same for mybox2, setting its dimensions to 2, 4, and 6.
   • vol = mybox1.volume();: This line calls the volume method on mybox1. The method calculates 5 * 10 * 15 and returns the result, which is then stored in the vol variable.
   • System.out.println("Volume is " + vol);: This prints the calculated volume of mybox1 to the console.
   • vol = mybox2.volume();: This calls the volume method on mybox2, calculates its volume (2 * 4 * 6), and stores the result in vol.
   • System.out.println("Volume is " + vol);: This prints the calculated volume of mybox2 to the console.

In essence, this program defines a Box blueprint, creates two specific Box objects, sets their individual dimensions using a method that accepts parameters, and then calculates and displays their volumes using another method.

Algorithm

The algorithm implemented in this code can be described as follows:

1. Define a Class Box:

   • Declare instance variables for width, height, and depth (all of type double).
   • Define a method volume() that calculates and returns the product of width, height, and depth.
   • Define a method setDim(double w, double h, double d) that accepts three double parameters and assigns them to the object's width, height, and depth instance variables, respectively.

2. Create a Main Program Class BoxDemo4:

   • Entry Point: Implement the main method.
   • Object Instantiation: Create two objects, mybox1 and mybox2, of the Box class.
   • Variable Declaration: Declare a double variable vol to hold volume values.
   • Set Dimensions for mybox1: Call the setDim method on mybox1 with arguments 5, 10, and 15.
   • Set Dimensions for mybox2: Call the setDim method on mybox2 with arguments 2, 4, and 6.
   • Calculate and Display Volume for mybox1:
     • Call the volume method on mybox1.
     • Store the returned volume in the vol variable.
     • Print the value of vol to the console, prefixed with "Volume is ".
   • Calculate and Display Volume for mybox2:
     • Call the volume method on mybox2.
     • Store the returned volume in the vol variable.
     • Print the value of vol to the console, prefixed with "Volume is ".