Example: Maximum Handshakes Calculator in Java

// Maximum Handshakes Calculator
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Create a Scanner object to read user input
        Scanner scanner = new Scanner(System.in);

        // Step 2: Prompt the user to enter the number of people
        System.out.print("Enter the number of people: ");

        // Step 3: Read the number of people from the user
        int numberOfPeople = scanner.nextInt();

        // Step 4: Validate input to ensure it's non-negative
        if (numberOfPeople < 0) {
            System.out.println("Number of people cannot be negative.");
        } else {
            // Step 5: Calculate the maximum number of handshakes using the formula
            // The formula is n * (n - 1) / 2, where n is the number of people.
            // This represents "n choose 2" combinations.
            long maxHandshakes = (long) numberOfPeople * (numberOfPeople - 1) / 2;

            // Step 6: Print the result
            System.out.println("Maximum number of handshakes: " + maxHandshakes);
        }

        // Step 7: Close the scanner to prevent resource leaks
        scanner.close();
    }
}