How to type some text in hidden field in Selenium WebDriver using Java

Question

I am using WebDriver with Java for test automation. I have the following HTML code for input field which is hidden:

Answer 1

WebDriver driver=new FirefoxDriver();
driver.get("http://localhost/login.do");
driver.manage().window().maximize();
RemoteWebDriver r=(RemoteWebDriver) driver;
String s1="document.getElementById('username').value='admin'";
r.executeScript(s1);