gistfile1.txt

// Bad example of static variable, In this case the
// driver instance can be accessed by multiple threads and
// potentially can be changed by multiple threads.
// This results into an unexpected behaviour at runtime when
// this code runs in parallel
class WebDriverContainer
{
  public static WebDriver driver; // No thread safety
}

// Keep in mind that a webdriver instance will be different for each thread.
// You cannot share the same instance to multiple tests running in different threads
// at the same time. This will result into unexpected results. What does it mean ?
// It means that we need to manage multiple instances of WebDriver for each thread.
// Here is an example to do this via a factory/manager class

class WebDriverManager
{
  private static List<int, WebDriver> driverList = new ArrayList<int, WebDriver>(); // A better alternative could be ThreadLocal class
  
  // GetDriver method is synchronized and is thread safe.
  public static synchronised WebDriver GetDriver(String webdriverName)
  {
    if(webdriverName.equals("Chrome")
    {
      // Firt get the threadID
      int threadId = Thread.currentThread().getId()
      // Check if the driverList already has a driver for this thread
      if(driverList.has(threadId))
      {
        return driverList.get(threadId);
      }
      // If we already dont have a webdriver instance for this thread
      // we will create one and add in the List. After that we will return
      // that instance of webdriver
      WebDriver driver = new ChromeDriver();
      driverList.add(threadId, driver);
      return driver;
    }
  }