How to Pressing Enter Button, ARROW_DOWN, ARROW_UP of Keyboa

import java.util.concurrent.TimeUnit;

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


public class KeysTest {

        public static void main(String[] args) {
            WebDriver myTestDriver = new FirefoxDriver();
            myTestDriver.get("http://tinyurl.com/yhu7olp");
            myTestDriver.manage().window().maximize();
            myTestDriver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys("a");
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);

            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);

            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);

            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_DOWN);
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_UP);
            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ARROW_UP);



            myTestDriver.findElement(By.xpath("//input[@class='ui-autocomplete-input']")).sendKeys(Keys.ENTER);

            myTestDriver.quit();

        }

}