Selenium Webdriver sessionId or check if all browser windows are closed

Just set

driver=null; 

everytime you quit the browser and than check

if (browser!=null){  //Attention: this comand is not supported  //as far as i know ;)  driver.doSomething();}

or

try{}catch (NullPointerException e)    e.printStackTrace();    System.err.print"DAMN";}

or receive a NullPointerException ;)

public bool InstanceExist    {        get        {            if (Instance != null)            {                try                {                    return (Instance.WindowHandles != null); // allways returns true if browser instance exist or thrown error                }                catch (Exception e)                {                    return false;                    // means that browser was closed by user                }            }            return false; // means that it wasn't created yet or was closed by developer programmally        }    }

You need to check 3 situations:

1. driver wasnt created
2. driver was closed by developer
3. browser was closed by user, but driwer instance still exists

All of those situations is checked with this code.

I think the cleanest way to detect if all windows are closed is smth like:

boolean allWindowsClosed = webDriver.getWindowHandles().isEmpty();

getWindowHandles returns a set of window handles for all open windows - see http://selenium.googlecode.com/git/docs/api/java/org/openqa/selenium/WebDriver.html#getWindowHandles()