Example: Count Numbers with Exactly 9 Divisors (Brute Force) in Java

// Count Numbers with Exactly 9 Divisors (Brute Force)
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {

    // Function to count divisors of a number
    public static int countDivisors(int n) {
        int count = 0;
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                if (i * i == n) {
                    count++;
                } else {
                    count += 2;
                }
            }
        }
        return count;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter the upper limit (N): ");
        int N = scanner.nextInt();
        scanner.close();

        int numbersWithNineDivisors = 0;

        // Step 1: Iterate through each number from 1 to N
        for (int i = 1; i <= N; i++) {
            // Step 2: Count divisors for the current number
            int divisors = countDivisors(i);
            // Step 3: Check if the count is exactly 9
            if (divisors == 9) {
                numbersWithNineDivisors++;
                System.out.println(i + " has exactly 9 divisors.");
            }
        }

        System.out.println("Total numbers up to " + N + " with exactly 9 divisors: " + numbersWithNineDivisors);
    }
}