For conditions 2 and 3 getting error Class cast exception Any solution

Question

public class ScrollingPage {

public static void main(String[] args) throws InterruptedException {

System.setProperty("webdriver.chrome.driver","C:\\Drivers\\chromedriver_win32\\chromedriver.exe");

WebDriver driver=new ChromeDriver();

driver.get("https://www.countries-ofthe-world.com/flags-of-the-world.html");

driver.manage().window().maximize();

JavascriptExecutor js=(JavascriptExecutor)driver;

//1. Scroll down page by pixel

// js.executeScript("window.scrollBy(0,1500)","");

// Long value=(Long)js.executeScript("return window.pageYOffset;");

// System.out.println("Number of pixels scrolled:"+value);

   //2. Scroll down page till element is visible

// WebElement flag=driver.findElement(By.xpath("//tbody/tr[91]/td[1]/img[1]"));

//

//  

//     js.executeScript("arguments[0].scrollIntoView();",flag);

// Long value=(Long)js.executeScript("return window.pageYOffset;");

// System.out.println("Number of pixels scrolled:"+value);

//

//3.End of the page

js.executeScript("window.scrollBy(0,document.body.scrollHeight)");

Long value=(Long)js.executeScript("return window.pageYOffset;");

    System.out.println("Number of pixels scrolled:"+value);

      Thread.sleep(5000);

      js.executeScript("window.scrollBy(0,-document.body.scrollHeight)");  //move to initial point

_________CONSOLE WINDOW______

Exception in thread "main" java.lang.ClassCastException: class java.lang.Double cannot be cast to class java.lang.Long (java.lang.Double and java.lang.Long are in module java.base of loader 'bootstrap') at .ScrollingPage.main(ScrollingPage.java:39)