Java program to check whether number is prime or not

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

Java program to check whether number is prime or not

Prime numbers are those numbers which cannot be divided by other numbers than 1 or itself. Example : 2, 3, 5, 7, 11, 13, 17….

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

Here’s the java code to check if number is prime or not using if else.

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

program to check whether the given number is prime or not using while loop

Here’s the program to check whether a number is prime or not using for loop 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.