how to verify popup message in selenium

how to verify alert and  popup message in selenium

package automationtesting;

import org.openqa.selenium.Alert;

import org.openqa.selenium.By;

import org.openqa.selenium.WebDriver;

import org.openqa.selenium.chrome.ChromeDriver;

public class AlertandPopup {

       public static void main(String[] args) throws InterruptedException {

              // TODO Auto-generated method stub

             

              System.setProperty("webdriver.chrome.driver","D:\\Sandeep\\Soft\\chromedriver.exe");

              WebDriver driver= new ChromeDriver();

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

              driver.get("https://www.seleniumeasy.com/test/javascript-alert-box-demo.html");

       driver.findElement(By.xpath("//*[@id=\"easycont\"]/div/div[2]/div[3]/div[2]/button")).click();

                 

       Alert alrt = driver.switchTo().alert();

           Thread.sleep(5000);

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

   

           if (gtxt.equals("Please enter your name")) {

            System.out.println(gtxt);

           }

            else {

               System.out.println("false");

            }

           driver.switchTo().alert().sendKeys("Text");

    driver.switchTo().alert().dismiss();

           Thread.sleep(5000);

    driver.quit();

}

}