How to verify if alert/warning/message is displayed in Selenium Webdriver in Java?

How to verify if alert/warning/message is displayed in Selenium Webdriver in Java?

package com.snapdeal;

import java.util.concurrent.TimeUnit;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.firefox.FirefoxDriver;

public class TestIsDisplayed {
public static void main(String[] args) {
WebDriver driver = new FirefoxDriver();
try {
driver.get(“https://accounts.google.com/ServiceLoginAuth”);
driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);
driver.findElement(By.id(“signIn”)).click();
WebElement e = driver.findElement(By
.xpath(“//*[@id='errormsg_0_Email']“));
boolean actual = e.isDisplayed();
if (actual) {
System.out.println(“Message is Displayed”);
// Get the warning message text
String testdata = driver.findElement(
By.xpath(“//*[@id='errormsg_0_Email']“)).getText();
System.out.println(“Test message is : ” + testdata);
} else {
System.out.println(“Message is not Displayed”);

}

} catch (Exception ex) {
System.out.println(“Exception” + ex.getMessage());

} finally {
driver.close();
}
}
}

/*

Output is

Message is Displayed
Test message is : Enter your email address.

*/