my code is not working properly?

here is my code. WebDriverWait wait = new WebDriverWait(driver, 10); Alert alert = wait.until(ExpectedConditions.alertIsPresent());

       //Accepting alert.
       alert.accept();
       System.out.println("Accepted the alert successfully.");
    }catch(Throwable e){
       System.err.println("Error came while waiting for the alert popup. "+e.getMessage());
    }

error showing like: Error came while waiting for the alert popup. Expected condition failed: waiting for alert to be present (tried for 10 second(s) with 500 MILLISECONDS interval)