1  import java.util.Scanner;
  2  
  3  public class PrimeNumbers {
  4    public static void main(String[] args) {
  5      Scanner input = new Scanner(System.in);
  6      System.out.print("Find all prime numbers <= n, enter n: ");
  7      int n = input.nextInt();
  8  
  9      final int NUMBER_PER_LINE = 10; // Display 10 per line
 10      int count = 0; // Count the number of prime numbers
 11      int number = 2; // A number to be tested for primeness
 12  
 13      System.out.println("The prime numbers are:");
 14  
 15      // Repeatedly find prime numbers
 16      while (number <= n) {
 17        // Assume the number is prime
 18        boolean isPrime = true; // Is the current number prime?
 19  
 20        // ClosestPair if number is prime
 21        for (int divisor = 2; divisor <= (int)(Math.sqrt(number)); 
 22            divisor++) {
 23          if (number % divisor == 0) { // If true, number is not prime
 24            isPrime = false; // Set isPrime to false          
 25            break; // Exit the for loop
 26          }
 27        }
 28  
 29        // Print the prime number and increase the count
 30        if (isPrime) {
 31          count++; // Increase the count
 32  
 33          if (count % NUMBER_PER_LINE == 0) {
 34            // Print the number and advance to the new line
 35            System.out.printf("%7d\n", number);
 36          }
 37          else
 38            System.out.printf("%7d", number);
 39        }
 40  
 41        // Check if the next number is prime
 42        number++;
 43      }
 44      
 45      System.out.println("\n" + count + 
 46        " prime(s) less than or equal to " + n);
 47    }
 48  }