Selenium WebDriver : How to handle PopUp and close it

/*
 * Pop-up handling in Selenium WebDriver
 * Programming language : JAVA
 * 
 * Here we will browse Rediff site and close the pop-up .
 * We will print the pop-up window URL and the main window URL 
 */

import java.util.Iterator;
import java.util.Set;

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

public class PopUpHandling {

 public static void main(String[] args) {
  WebDriver driver = new FirefoxDriver();
  
  // for chrome browser setting
  //System.setProperty("webdriver.chrome.driver", "D:/setup/chromedriver.exe");
  //WebDriver driver = new ChromeDriver();
  
  driver.get("http://www.rediff.com/");
  
  // Since the Window Handles are unique , we will use java.util.Set to store as it does allow the duplicate values. 
  // Windows Handles is of type String, so we store the value of window handle as String in Set
  Set<String> winHandle = driver.getWindowHandles();
  
  // just to check the number of total windows , in this case its 2
  System.out.println("Total number of Windows : "+ winHandle.size()); 
  
  // Iterator is use to iterator through Set , we can use for loop also
  Iterator<String> it = winHandle.iterator();
  
  String parentWindow = it.next();  
  
  
  String childWindow = it.next();   
  
  // switch to child window / pop-up window
  driver.switchTo().window(childWindow); 
  
  System.out.println("child URL/ Title : " + driver.getCurrentUrl() );
  driver.close(); // close the child /popUp window

  driver.switchTo().window(parentWindow);
  System.out.println("parent URL/ Title : " + driver.getCurrentUrl() );
  
 }

}