Java program to check whether number is prime or not

Let’s learn java program to check whether number is prime or not.

Java program to check whether number is prime or not

Prime number program in java is one of the most asked interview question.

A prime number is a number that is greater than one and divided by one or itself.

Prime numbers are those numbers which cannot be divided by other numbers than 1 or itself.

Example : 2, 3, 5, 7, 11, 13, 17….

Here’s the program to check whether number is prime or not using if else statement.

public class PrimeNumberInJava
{
   public static void main(String[] args)
   {
      int a, b = 0, flag = 0;
      int number = 66;
      b = number / 2;
      if(number == 0 || number == 1)
      {
         System.out.println(number + " is not prime number");
      }
      else
      {
         for(a = 2; a <= b; a++)
         {
            if(number % a == 0)
            {
               System.out.println(number + " is not prime number.");
               flag = 1;
               break;
            }
         }
         if(flag == 0)
         {
            System.out.println(number + " is prime number.");
         }
      }
   }
}


Output:

java program to check whether number is prime or not

prime number program in java using while loop

Similarly let’s see prime number program in java using while loop.

import java.util.Scanner;
public class PrimeNumberUsingWhileLoop
{
   public static void main(String[] args)
   {
      boolean checkPrime = true;
      Scanner sc = new Scanner(System.in);
      System.out.println("Please enter any number: ");
      int number = sc.nextInt();
      int a = 2;
      while(a <= number / 2)
      {
         if(number % a == 0)
         {
            checkPrime = false;
            break;
         }
         a++;
      }
      if(checkPrime)
      {
         System.out.println(number + " is a prime number.");
      }
      else
      {
         System.out.println(number + " is not a prime number.");
      }
      sc.close();
   }
}


Output:

Please enter any number: 17
17 is a prime number.


NOTE: 2 is the only even prime number. 0 and 1 are not prime numbers.