How to solve this problem using if-else loop in java selenium?

If variable value between j =<10 then page through error "Sorry ! user already..."
and then I try to assign another random value to variable k and fill up form again.

I want to execute driver.findElement(By.xpath("//*[contains(text(),'Sorry ! ')]")).isDisplayed() step only if I get error. Else just print success message.

Problem here is even if I get success message I'm getting element not found error due to driver.findElement(By.xpath("//*[contains(text(),'Sorry ! ')]")).isDisplayed().
I also tried implementing boolean Sorry_Error = driver.findElement(By.xpath("//*[contains(text(),'Sorry ! ')]")).isDisplayed(); but I think it is similar logic just different way of implementation. if there is no error then loop should go for else block but insted it searching .isDisplayed xpath and throwing error.
Isn't it correct way to handle user already exist error or is there any other logic.

This is success message

This is error message

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-html -->

package com.self.learn;

import java.util.Random;
import java.util.concurrent.TimeUnit;

import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.WebDriverWait;
import org.testng.annotations.Test;

public class testandquiz {

	public static WebDriverWait wait;

	@Test
	public void Simple_Test() throws InterruptedException {

		System.setProperty("webdriver.chrome.silentOutput", "true");
		System.setProperty("webdriver.chrome.driver", "src/main/resources/chromedriver.exe");
		WebDriver driver = new ChromeDriver();
		wait = new WebDriverWait(driver, 10);
		driver.manage().deleteAllCookies();

		driver.get("https://www.testandquiz.com/user-registration");
		driver.manage().window().maximize();
		driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
		((JavascriptExecutor) driver).executeScript("scroll(0,300)");

		WebElement Fname = driver.findElement(By.id("first_name"));
		WebElement Lname = driver.findElement(By.id("last_name"));
		WebElement User_name = driver.findElement(By.id("user_name"));
		WebElement email_address = driver.findElement(By.id("email_address"));
		WebElement password = driver.findElement(By.id("password"));
		WebElement re_password = driver.findElement(By.id("re_password"));
		WebElement city = driver.findElement(By.id("city"));
		WebElement state = driver.findElement(By.id("state"));
		WebElement country = driver.findElement(By.id("country"));
		WebElement pin_code = driver.findElement(By.id("pin_code"));
		WebElement contact_no = driver.findElement(By.id("contact_no"));

		Random randomGenerator = new Random();
		int j = 10;
		int k = 99999;
		int i = randomGenerator.nextInt(j);

		Fname.sendKeys("Test" + i + "");
		Lname.sendKeys("Test" + i + "");
		User_name.sendKeys("Test" + i + "");
		email_address.sendKeys("Test" + i + "");
		password.sendKeys("Test" + i + "");
		re_password.sendKeys("Test" + i + "");
		city.sendKeys("Test" + i + "");
		state.sendKeys("Test" + i + "");
		country.sendKeys("Test" + i + "");
		pin_code.sendKeys("Test" + i + "");
		contact_no.sendKeys("1234567890");

		driver.findElement(By.xpath("//button[contains(text(),'Sign Up')]")).click();

		if (driver.findElement(By.xpath("//*[contains(text(),'Sorry ! ')]")).isDisplayed()) {

			WebElement Fname1 = driver.findElement(By.id("first_name"));
			WebElement Lname1 = driver.findElement(By.id("last_name"));
			WebElement User_name1 = driver.findElement(By.id("user_name"));
			WebElement email_address1 = driver.findElement(By.id("email_address"));
			WebElement password1 = driver.findElement(By.id("password"));
			WebElement re_password1 = driver.findElement(By.id("re_password"));
			WebElement city1 = driver.findElement(By.id("city"));
			WebElement state1 = driver.findElement(By.id("state"));
			WebElement country1 = driver.findElement(By.id("country"));
			WebElement pin_code1 = driver.findElement(By.id("pin_code"));
			WebElement contact_no1 = driver.findElement(By.id("contact_no"));

			Fname1.clear();
			Fname1.sendKeys("Test" + k + "");
			Lname1.clear();
			Lname1.sendKeys("Test" + k + "");
			User_name1.clear();
			User_name1.sendKeys("Test" + k + "");
			email_address1.clear();
			email_address1.sendKeys("Test" + k + "");
			password1.clear();
			password1.sendKeys("Test" + k + "");
			re_password1.clear();
			re_password1.sendKeys("Test" + k + "");
			city1.clear();
			city1.sendKeys("Test" + k + "");
			state1.clear();
			state1.sendKeys("Test" + k + "");
			country1.clear();
			country1.sendKeys("Test" + k + "");
			pin_code1.clear();
			pin_code1.sendKeys("Test" + k + "");
			contact_no1.clear();
			contact_no1.sendKeys("1234567890");

			driver.findElement(By.xpath("//button[contains(text(),'Sign Up')]")).click();
		}

		else {

			String Message = driver.findElement(By.xpath("//div[contains(text(),'verification mail')]")).getText();
			System.out.println(Message);
		}

	}
}

<!-- end snippet -->

I don't know how to implement this logic.

You won't necessarily need a wait here... depends on if javascript updates the DOM. If it's after a standard page load, then just use:

   List<WebElement> elements = driver.findElements(By.xpath("//*[contains(text(), 'Sorry')]");
        if (elements.size() > 0)
            {
            // sorry found
            }
            else
            {
            // sorry not found
            }

Else use try/catch with a wait:

 try {
         WebDriverWait wait = new WebDriverWait(driver, 5);
         WebElement element =  wait.until(ExpectedConditions.visibilityOfElementLocated(By.xpath("//*[contains(text(), 'Sorry')]"));     
            // sorry found             
         }
         catch (Exception ex)
         {
         //sorry not found
         }

Use same logic for error text.