How to handle alert window?

 package wdProgram;

import java.util.concurrent.TimeUnit;

import org.openqa.selenium.By;

import org.openqa.selenium.WebDriver;

import org.openqa.selenium.chrome.ChromeDriver;

public class HandleAlertWindow {

public static void main(String[] args) {

System.setProperty("webdriver.chrome.driver",

"D:\\Software\\Testing-Tools\\Selenium\\WebDriver\\Drivers\\IEChromeFirefox\\19092018\\chromedriver.exe");

WebDriver driver = new ChromeDriver();

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

driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);

driver.get("http://localhost/uth/gadgetsgallery/catalog");

driver.findElement(By.linkText("create an account")).click();

driver.findElement(By.id("tdb1")).click();

String alertText = driver.switchTo().alert().getText();

System.out.println(alertText);

driver.switchTo().alert().accept();  //Clicks on OK button

//driver.switchTo().alert().dismiss();  //Clicks on CANCEL button

driver.findElement(By.name("firstname")).sendKeys("Tanmay");

}

}