Iterative Constructs in Java

Chapter 9

Iterative Constructs in Java

Class 10 - Logix Kips ICSE Computer Applications with BlueJ

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Java Program: Menu-Driven Program: Check Prime or Automorphic Number

26. Write a menu driven program to accept a number and check and display whether (i) it is a Prime Number or not (ii) it is an Automorphic Number or not. (Use switch-case statement).

(i). Prime number: A number is said to be a prime number if it is divisible only by 1 and itself and not by any other number. Example: 3, 5, 7, 11, 13 etc.

(ii). Automorphic number: An automorphic number is the number which is contained in the last digit(s) of its square. Example: 25 is an automorphic number as its square is 625 and 25 is present as the last two digits.

Program Title: Check Prime or Automorphic Number

Java

import java.util.Scanner;
 
public class PrimeAutomorphic {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
 
        System.out.println("MENU");
        System.out.println("1. Check Prime Number");
        System.out.println("2. Check Automorphic Number");
        System.out.print("Enter your choice: ");
        int choice = sc.nextInt();
 
        System.out.print("Enter a number: ");
        int num = sc.nextInt();
 
        switch (choice) {
            case 1:
                // Check Prime
                if (num <= 1) {
                    System.out.println(num + " is NOT a Prime Number.");
                    break;
                }
                boolean isPrime = true;
                for (int i = 2; i <= Math.sqrt(num); i++) {
                    if (num % i == 0) {
                        isPrime = false;
                        break;
                    }
                }
                if (isPrime) {
                    System.out.println(num + " is a Prime Number.");
                } else {
                    System.out.println(num + " is NOT a Prime Number.");
                }
                break;
 
            case 2:
                // Check Automorphic
                int square = num * num;
                int temp = num;
                boolean isAutomorphic = (square % (int) Math.pow(10, String.valueOf(num).length()) == num);
 
                if (isAutomorphic) {
                    System.out.println(num + " is an Automorphic Number.");
                } else {
                    System.out.println(num + " is NOT an Automorphic Number.");
                }
                break;
 
            default:
                System.out.println("Invalid choice! Please select 1 or 2.");
        }
 
        sc.close();
    }
}

Output

Sample Output 1 (Prime Number)
MENU
1. Check Prime Number
2. Check Automorphic Number
Enter your choice: 1
Enter a number: 17
17 is a Prime Number.

Sample Output 2 (Automorphic Number) 
MENU
1. Check Prime Number
2. Check Automorphic Number
Enter your choice: 2
Enter a number: 25
25 is an Automorphic Number.

📝 Explanation

Prime Number Check:

Numbers ≤ 1 are not prime.
Check divisibility up to √num for efficiency.

Automorphic Number Check:

A number is automorphic if its square ends with the number itself.
Use modulus with 10^number_of_digits to check.

Switch-Case handles menu selection.
Default handles invalid choices.