Selenium Webdriver (Java) - Scroll Up and Down

For Scroll Down:

WebDriver driver = new FirefoxDriver();
JavascriptExecutor jse = (JavascriptExecutor)driver;
jse.executeScript("window.scrollBy(0,250)", "");

OR, you can do as follows:

jse.executeScript("scroll(0, 250);");

For Scroll up:

jse.executeScript("window.scrollBy(0,-250)", "");
OR,
jse.executeScript("scroll(0, -250);");