How to download files using GeckoDriver Firefox and Selenium?

I used this code for download file , but its not working

FirefoxProfile profile = new FirefoxProfile();

profile.setPreference("browser.download.dir","D:\\WebDriverDownloads");
profile.setPreference("browser.download.folderList", 2);
profile.setPreference("browser.helperApps.neverAsk.saveToDisk","application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;"); 
profile.setPreference( "browser.download.manager.showWhenStarting",false );
profile.setPreference( "pdfjs.disabled",true );


FirefoxDriver driver = new FirefoxDriver(profile);  //Shows error on this line

driver.get("http://toolsqa.com/automation-practice-form/");

driver.findElement(By.linkText("Test File to Download")).click();

Thread.sleep(5000);

It gives me error

And when I remove

'Profile'

form this FirefoxDriver driver = new FirefoxDriver(profile); then code run successfully but download files window is not closing and file also not downloading.

Instead of this I use Robot

Robot object=new Robot();
object.keyPress(KeyEvent.VK_DOWN);
object.keyRelease(KeyEvent.VK_DOWN);         
object.keyPress(KeyEvent.VK_ENTER);
object.keyRelease(KeyEvent.VK_ENTER);

and its working fine.But Why my above code is not working?

To download the file clicking on the link with text as Test File to Download you need to:

• Create a new FirefoxProfile() and set the required preferences.
• Use an instance of FirefoxOptions() set the profile.

• You can use the following solution:

  System.setProperty("webdriver.gecko.driver", "C:\\Utility\\BrowserDrivers\\geckodriver.exe");
  FirefoxProfile profile = new FirefoxProfile();
  profile.setPreference("browser.download.dir", "C:\\Utility\\Downloads");
  profile.setPreference("browser.download.folderList",2);
  profile.setPreference("browser.helperApps.neverAsk.saveToDisk", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
  profile.setPreference("browser.download.manager.showWhenStarting", false);
  profile.setPreference("browser.helperApps.neverAsk.openFile","application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
  profile.setPreference("browser.helperApps.alwaysAsk.force", false);
  profile.setPreference("browser.download.manager.useWindow", false);
  profile.setPreference("browser.download.manager.focusWhenStarting", false);
  profile.setPreference("browser.download.manager.showAlertOnComplete", false);
  profile.setPreference("browser.download.manager.closeWhenDone", true);
  FirefoxOptions options = new FirefoxOptions();
  options.setProfile(profile);
  WebDriver driver = new FirefoxDriver(options);
  driver.get("http://toolsqa.com/automation-practice-form/");
  new WebDriverWait(driver, 20).until(ExpectedConditions.elementToBeClickable(By.linkText("Test File to Download"))).click();