我无法单击“ clikElement”按钮，并收到异常消息，指出“ elementclickinterceptedexception无法点击”

Question

public static void main(String[] args) throws InterruptedException {   
    WebDriver driver = new FirefoxDriver();
    driver.get("http://toolsqa.com/automation-practice-switch-windows/");    
    WebElement clickElement = driver.findElement(By.id("button1")); 
    for(int i = 0; i < 3; i++) {
       clickElement.click();
       Thread.sleep(3000);
    }
}