prime numbers upto n in java code example

Example 1: java prime numbers

public class Main {
  public static void main(String[] args) {
    for (int i = 2; i < 1_000_000; ++i) {
      boolean isPrime = true;
      int sqrt = (int)Math.ceil(Math.sqrt(i));
      for (int divisor = 2; divisor <= sqrt; ++divisor) {
        if (i % divisor == 0) {
          isPrime = false;
          break;
        }
      }
      if (isPrime) {
        System.out.println(i);
      }
    }
  }
}

Example 2: Java program to print prime numbers upto n

// Java program to print prime numbers upto n
import java.util.Scanner;
public class PrimeNumberUptoN
{
   public static void main(String[] args)
   {
      Scanner sc = new Scanner(System.in);
      int a = 0;
      int n = 0;
      String strPrime = "";
      System.out.println("Please enter the value of n: ");
      int number = sc.nextInt();
      for(a = 1; a <= number; a++)
      {
         int counter = 0;
         for(n = a; n >= 1; n--)
         {
            if(a % n == 0)
            {
               counter = counter + 1;
            }
         }
         if(counter == 2)
         {
            strPrime = strPrime + a + " ";
         }
      }
      System.out.println("prime numbers upto n are: ");
      System.out.println(strPrime);
      sc.close();
   }
}