import java.util.InputMismatchException; import java.util.Scanner; /** * To check whether a given number is prime */ public class PrimeCheck { public static void main(String[] args) { // Accept input from the console System.out.print("Please enter a natural number: "); int num = 0; try { Scanner sc = new Scanner(System.in); num = sc.nextInt(); sc.close(); } catch (InputMismatchException e) { outputAndEnd("Input not valid, expected a natural number."); // Error message for all non numerical inputs } if (num < 0) { outputAndEnd("Input not valid, natural number expected"); // Error message for all negative inputs } else if (num < 2) { outputAndEnd("0 and 1 are neither prime nor composite"); // Info message for 0 and 1 } // Check if the given number is divisible from any number between 2 and num/2, if so, its composite for (int i = 2; i <= num / 2; i++) { if (num % i == 0) { outputAndEnd(num + " is not a prime number."); // Output result and exit as we found one divisor other than 1 and itself } } // The number has exit the loop with no divisors, which means it is a prime number, print success message. outputAndEnd(num + " is a prime number."); } // A method to print the given message and exit the program private static void outputAndEnd(String message) { System.out.println(message); // output the given message System.exit(0); // exit the program } }