While running it is not recognizing the xpath

Question

Hi, I am able to find/write xpath for below webelement,but while running the test it is not recognizing it. Tried with both implicitwait and thread.sleep. Can anyone help me to sort this out.

It is a selection list box:
//span[@class='mat-select-placeholder ng-tns-c25-18 ng-star-inserted']

HTML:

<div class="mat-select-value" xpath="1">
<!---->
<span class="mat-select-placeholder ng-tns-c25-18 ng-star-inserted" style="">&nbsp;</span>
<!---->
</div>

Code:
        try {
            
            Thread.sleep(10000);
             JavascriptExecutor js = (JavascriptExecutor)dr;
             js.executeScript("window.scrollTo(0, document.body.scrollHeight)");
                WebElement element1 = wait.until(ExpectedConditions.visibilityOfElementLocated(By.xpath("//div[@class='mat-select-value']//span[@class='mat-select-placeholder ng-tns-c25-18 ng-star-inserted']")));

System.out.println("Yes2");
            Select s=new Select(element1);
            s.selectByIndex(1);
            Thread.sleep(2000);
            System.out.println("Yes3");
        }
        catch(NoSuchElementException e)
        {
            System.out.println("no");
        }

Answer 1

There are two parts to this. The first is that you need to be sure that your XPath is correct. 

You can probably use a tool like Firefinder (a firefox extension for Firebug) to validate the XPath. 

Navigate to your page and be sure the element you need is present and then hit f12 and go to the FireFinder section. Enter in the XPath you are using and see if it can be found.

Assuming your XPath is correct then you might want to investigate using an explicit wait if for some reason you are waiting on the page element to load.

Example:

   WebDriverWait wait = new WebDriverWait(_driver, 10);
   wait.until(ExpectedConditions.visibilityOf(........));