Java program print prime numbers

This java program prints prime numbers, number of prime numbers required is asked from the user. Remember that smallest prime number is 2.

Java programming code

import java.util.*;
 
class PrimeNumbers
{
   public static void main(String args[])
   {
      int n, status = 1, num = 3;
 
      Scanner in = new Scanner(System.in);
      System.out.println("Enter the number of prime numbers you want");
      n = in.nextInt();
 
      if (n >= 1)
      {
         System.out.println("First "+n+" prime numbers are :-");
         System.out.println(2);
      }
 
      for ( int count = 2 ; count <=n ;  )
      {
         for ( int j = 2 ; j <= Math.sqrt(num) ; j++ )
         {
            if ( num%j == 0 )
            {
               status = 0;
               break;
            }
         }
         if ( status != 0 )
         {
            System.out.println(num);
            count++;
         }
         status = 1;
         num++;
      }         
   }
}

Download Prime numbers program class file.

Output of program:
prime numbers

We have used sqrt method of Math package which find square root of a number. To check if an integer(say n) is prime you can check if it is divisible by any integer from 2 to (n-1) or check from 2 to sqrt(n), first one is less efficient and will take more time.

randomness