import static javax.swing.JOptionPane.*;

public class primtall2 { //class start

// part 1 - get the user input
public static int getInput(){
        String tallinput = showInputDialog("Skriv inn et tall");
        int number = Integer.parseInt(tallinput);
        return number;
}


// part 2 - check if the number is prime

// functions are run from top to bottom, so it's perfectly okay to just quit early
// an early return like this is much more readable than nested ifs
public static boolean checkPrime(int number){
        if(number == 2) return true;
        if(number == 1) return true;
        if(number%2==0) return false;
        int maxNumber = (int)Math.floor(Math.sqrt(number));
        for(int i = 3; i <= maxNumber; ++i){
                if( number % i == 0) return false;
        }
        // no primes found;
        return true;
}

// part 3 - notify the user

public static void notifyUser(boolean numberIsPrime, int number){
        if(numberIsPrime){
                showMessageDialog(null, "Tallet "+number+" er et primtall");
        }
        else{
                showMessageDialog(null, "Tallet "+number+" er ikke et primtall");
        }
}


public static void main(String[] args){
        // lets tie it all together!
        // read user inputs  one after the other, let the user know the results
        int tallinput = 1; // lets define this here first to force the program run at least once
        while (tallinput > 0){ //kjører programmet på nytt med mindre brukeren trykker cancel.
                tallinput = getInput();
                boolean isPrime = checkPrime(tallinput);
                notifyUser(isPrime, tallinput);
        }
        return;
    }
}