NullPointerException while accessing WebDriverWait instance

Question

In my test framework, I have a DriverInitializer class that initializes the WebDriver and WebDriverWait instances (instead of initializing it on every class). The page object classes extend this class to access the WebDriver.

I'm getting a nullpointer exception thrown while trying to access the WebDriverWait instance. See void method init_webdriver_wait below:

public class DriverInitializer {
 protected WebDriver driver;
 protected WebDriverWait wdw;
 protected final long timeInSeconds = 30;
 public DriverInitializer(WebDriver driver) {
 this.driver = driver;
 }
 public WebDriver getDriver() {
 return driver;
 }
 public PropertyConfig goToHome() {
 PropertyConfig pc = new PropertyConfig(driver);
 pc.getAppUrl();
 return pc;
 }
 public void init_webdriver_wait() {
 try {
 wdw = new WebDriverWait(driver, timeInSeconds); 
 }
 catch(Exception e) {
 // This error message is being triggered
 // and always says that the WebDriverWait instance is null.
 System.out.println("Error in DriverInitializer " + e.getMessage());
 } 
 }
}

In my second class, the LandingPage page factory class, I extended the DriverInitializer class:

 public class LandingPage extends DriverInitializer { 
 @FindBy(how=How.LINK_TEXT, using="REGISTER")
 WebElement register_link;
 @FindBy(how=How.LINK_TEXT, using="LOGIN")
 WebElement login_link;
 public LandingPage(WebDriver driver) {
 super(driver);
 PageFactory.initElements(driver, this);
 }
 public void locate_register_link() throws InterruptedException {
 try {
 init_webdriver_wait(); 
 if(wdw != null) {
 // Sample check if the WebDriverWait instance is null.
 wdw.until(ExpectedConditions.elementToBeClickable(register_link));
 Thread.sleep(3000); 
 }
 else {
 // This error message is triggered.
 // It says that the WebDriverWait instance is null.
 System.out.println("WDW is null -> LandingPage.java");
 }
 }
 catch(Exception e) {
 System.out.println("Error in LandingPage => " + e.getMessage());
 }
 }
}

Why does it always return a null pointer exception on my WebDriverWait instance?

• FDM: Can you add the callstack?

Answer 1

`try{
 init_webdriver_wait();
 if(wdw != null){ // sample check if the webdriverwait instance is null
 wdw.until(ExpectedConditions.elementToBeClickable(register_link));
 Thread.sleep(3000);`

My guess would be that wdw is null because you never set a value to that variable. Could you try: WebdriverWait wdw = init_webdriver_wait();