isPrimeNumber

package datastructure;
import javax.swing.JOptionPane;
public class PrimeNumber
{
    public static void main(String arg[])
    {
        JOptionPane.showMessageDialog(null, PrimeNumber.isPrime(Integer.parseInt(JOptionPane.showInputDialog("Enter Number"))));
    }
    public static boolean isPrime(int num)
    {
        if (num<4)return true;
        if (num%2==0)return false;
        for(int d=3; d*d<=num;d+=2)
            if(num%d==0)return false;
        return true;
    }
}