How to add firebug to mozilla firefox through webdriver Code

File file = new File("firebug-1.8.1.xpi");

FirefoxProfile firefoxProfile = new FirefoxProfile();

firefoxProfile.addExtension(file);

firefoxProfile.setPreference("extensions.firebug.currentVersion", "1.8.1"); // Avoid 

startup screen

WebDriver driver = new FirefoxDriver(firefoxProfile);