java to print all prime numbers smaller than n code example

Example 1: Java program to print prime numbers from 2 to n

// Java program to print prime numbers from 2 to n
import java.util.Scanner;
public class PrimeNumberFrom2Ton
{
   public static void main(String[] args) 
   {
      int loop, max;
      System.out.print("Please enter highest (maximum) number: ");
      Scanner sc = new Scanner(System.in);
      max = sc.nextInt();
      for(loop = 2; loop < max; ++loop)
      {
         if(findPrime(loop))
         {
            System.out.println(loop);
         }
      }
      sc.close();
   }
   public static boolean findPrime(int number)
   {
      int a;
      boolean boolPrime = true;
      for(a = 2; a < number / 2; a++)
      {
         if(number%a == 0)
         {
            boolPrime = false;
            break;
         }
      }
      return boolPrime;
   }
}

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();
   }
}

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