Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java program is designed to demonstrate basic input/output operations, variable handling, and the use of a while loop to perform repetitive tasks. Specifically, it prompts the user to enter five integer numbers, calculates their sum, and then computes their average.

Here's a step-by-step breakdown of its logic:

1. Import Scanner: The line import java.util.Scanner; brings in the Scanner class, which is a utility in Java used to read input from various sources, including the keyboard (System.in).
2. Class Definition: The code defines a class named prog17. In Java, all code resides within classes.
3. Main Method: The public static void main(String[] args) method is the entry point of any Java application. When you run this program, execution begins here.
4. Scanner Initialization: Scanner input = new Scanner(System.in); creates an object of the Scanner class, named input. This object is configured to read data from the standard input stream, which is typically your keyboard.
5. Variable Declaration and Initialization:
   • int i = 1; declares an integer variable i and initializes it to 1. This variable will serve as a counter for the loop, keeping track of how many numbers have been entered.
   • int sum = 0; declares an integer variable sum and initializes it to 0. This variable will accumulate the total of the numbers entered by the user.
6. Initial Prompt: System.out.println("Enter 5 numbers:"); displays a message on the console, instructing the user about the program's requirement.
7. The while Loop:
   • while(i <= 5): This is the core of the repetitive logic. The code inside the curly braces {} will execute repeatedly as long as the condition i <= 5 is true.
   • Inside the loop (Iteration):
     • System.out.print("Number " + i + ": "); prompts the user to enter a specific number (e.g., "Number 1:", "Number 2:", etc.). System.out.print is used here instead of println to keep the user's input on the same line as the prompt.
     • sum += input.nextInt(); reads the integer value typed by the user from the keyboard using input.nextInt() and adds it to the current value of sum. This is a shorthand for sum = sum + input.nextInt();.
     • i++; increments the counter variable i by 1. This is crucial; without it, i would never change, and the loop condition i <= 5 would always be true (if i started at 1), leading to an infinite loop.
8. Calculating Average: After the loop finishes (i.e., i becomes 6, making i <= 5 false), the program proceeds to calculate the average.
   • double avg = sum / 5.0; calculates the average. It's important to note 5.0 here. If it were 5 (an integer), Java would perform integer division, potentially truncating any decimal part. By using 5.0 (a double), Java performs floating-point division, ensuring an accurate average with decimal places, and the result is stored in a double variable avg.
9. Displaying Results:
   • System.out.println("Sum = " + sum); prints the final calculated sum to the console.
   • System.out.println("Average = " + avg); prints the calculated average to the console.
10. Closing Scanner: input.close(); is a good practice to release the system resources associated with the Scanner object, preventing potential resource leaks.

Algorithm

The algorithm used in this program can be described in the following steps:

1. Start: Begin the program execution.
2. Initialize Scanner: Create a Scanner object to read input from the standard input stream (keyboard).
3. Initialize Variables:
   • Set a counter variable i to 1.
   • Set a sum variable sum to 0.
4. Prompt User: Display a message asking the user to enter 5 numbers.
5. Loop for Input and Summation (While loop):
   • Condition Check: While the counter i is less than or equal to 5, continue to the next step. Otherwise, exit the loop.
   • Prompt for Number: Display a prompt asking for the i-th number.
   • Read Input: Read the integer value entered by the user.
   • Accumulate Sum: Add the read number to the sum variable.
   • Increment Counter: Increase the value of i by 1.
   • Repeat: Go back to the Condition Check step.
6. Calculate Average: After the loop terminates, divide the sum by 5.0 (to ensure floating-point division) and store the result in a double variable avg.
7. Display Sum: Print the final value of sum to the console.
8. Display Average: Print the final value of avg to the console.
9. Close Scanner: Release the resources held by the Scanner object.
10. End: Terminate the program.