import java.math.*;
import java.util.Scanner;

public class CheckPrimeNumber {

    final static BigInteger BIG_INTEGER_TWO = new BigInteger("2");

    public static void main(String[] args)
    {
        try{
            Scanner sc= new Scanner(System.in);
            System.out.println("Enter a valid positive number: ");
            String strinput=sc.nextLine();
            BigInteger input = new BigInteger(strinput);

            BigInteger num = input.divide(BIG_INTEGER_TWO);

            sc.close();

            boolean isPrime = isPrime(input);

            if (isPrime) {
                System.out.println(input +" is a prime number.");
            } else {
                System.out.println(input+" is not a prime number.");
            }
        }
        catch(Exception e){
            System.out.println("Please enter only valid positive number: ");
        }
        finally{
            System.out.println("Thank you...!!!");

        }
    }

    protected static boolean isPrime(BigInteger input) {
        boolean isPrime = false;

        if(input.equals(0)){
            isPrime = false;
        }

        if(input.equals(1)){
            isPrime = false;
        }
        else {
            int flag = 0;
            for (BigInteger one = BigInteger.ONE; one.compareTo(input.divide(BIG_INTEGER_TWO)) < 0; one = one.add(BigInteger.ONE)) {

// Above line is still giving the error. It cannot be converted from int to boolean.
// I understood what you suggested, but I am not able to implement that logic.

                if (input.remainder(BIG_INTEGER_TWO).equals(BigInteger.ZERO)) {
                    isPrime = false;
                    flag = 1;
                    break;
                }
            }
            if(flag==0) {
                isPrime = true;
            }
        }

        return isPrime;
    }

}