Sometimes it can be very useful to check if an element exists on a page. The code below demonstrates how to do that.
@Test
public void checkIfElementExists() {
driver.get("http://www.github.com");
if (driver.findElements(By.id("elementNotExists")).size() != 0) {
System.out.println("Element exist");
} else {
System.out.println("Element doesn't exist");
}
}