How to download pdf file from website in Selenium Webdriver using java.

 import java.io.BufferedInputStream;  
 import java.io.BufferedOutputStream;  
 import java.io.FileOutputStream;  
 import java.io.IOException;  
 import java.io.InputStream;  
 import java.io.OutputStream;  
 import java.net.MalformedURLException;  
 import java.net.URL;  
 import java.util.ArrayList;  
 import java.util.List;  
 import org.openqa.selenium.By;  
 import org.openqa.selenium.WebDriver;  
 import org.openqa.selenium.WebElement;  
 import org.openqa.selenium.htmlunit.HtmlUnitDriver;  
   
   
 public class pdffiledownloadfromwebsite {  
   
 public static void main(String[] args) throws MalformedURLException, IOException {  
  List<String> uniqurl = new ArrayList();  
   
 // Initialize Webdriver driver   
 WebDriver driver = new HtmlUnitDriver();  
 // Go to pdf page  
 driver.get("http://www.banglakitab.com/kitab.htm");  
 // get all page urls  
 List<WebElement> pdfurllist = driver.findElements(By.tagName("a"));  
   
 for (WebElement elemnet : pdfurllist) {  
 String pdfurl = elemnet.getAttribute("href").trim();  
 //check pdf url  
 if (pdfurl.contains(".pdf")) {  
 // check one file download one time  
 if (!(uniqurl.contains(pdfurl))) {  
  uniqurl.add(pdfurl);  
 //print file name and download url  
 System.out.println(filename(pdfurl) + " ---> " + pdfurl);  
 //download file  
 URL url = new URL(pdfurl);  
 InputStream in = new BufferedInputStream(url.openStream());  
 OutputStream out = new BufferedOutputStream(new FileOutputStream(filename(pdfurl)));  
   
 for (int i; (i = in.read()) != -1;) {  
 out.write(i);  
 }  
 in.close();  
 out.close();  
             
  }  
  }  
 }  
   
 // close driver   
 driver.quit();  
   
 }  
   
   // get file name. It depend on download url pattent.  
   private static String filename(String url) {  
     String filename = "";  
     String file[];  
   
     file = url.split("\\/");  
     if (file[file.length - 1].contains("-")) {  
       filename = file[file.length - 1].trim().replace("-", " ");  
     } else if (file[file.length - 1].contains("%20")) {  
       filename = file[file.length - 1].trim().replace("%20", " ");  
     } else {  
       filename = file[file.length - 1].trim();  
     }  
   
     return filename;  
   }  
   
 }