Module 14 - output for window handle is -1,-2

import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.TimeUnit;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;

public class Rediff {

public static void main(String[] args) {
// TODO Auto-generated method stub
WebDriver driver = new FirefoxDriver();
driver.manage().window().maximize();
driver.manage().timeouts().implicitlyWait(20, TimeUnit.SECONDS);
driver.manage().timeouts().pageLoadTimeout(15,TimeUnit.SECONDS);

Set<String> windowIds =driver.getWindowHandles();;
System.out.println("Total Window Opened: -"+windowIds.size());
Iterator<String> it = windowIds.iterator();
System.out.println(it.next());

System.out.println("---------------------");
driver.get("http://www.rediff.com/");
windowIds =driver.getWindowHandles();
System.out.println("Total Window Opened: -"+windowIds.size());
it = windowIds.iterator();
System.out.println(it.next());
System.out.println(it.next());
}

}
==========================================
OUTPUT I received

Total Window Opened: -1
{94b375b5-cddf-45f2-a5af-d94195cc9cab}
---------------------
Total Window Opened: -2
{94b375b5-cddf-45f2-a5af-d94195cc9cab}
{c7603b59-d426-48f5-93d0-247204b2bdeb}