How to check if an element exists in WebDriver selenium with java?.

 import java.util.concurrent.TimeUnit;  
 import org.openqa.selenium.By;  
 import org.openqa.selenium.WebDriver;  
 import org.openqa.selenium.firefox.FirefoxDriver;  
 public class Elementexists {  
 public static void main(String[] a) throws InterruptedException {  
     // Initialize driver  
     WebDriver driver = new FirefoxDriver();  
     //Maximize browser window   
     driver.manage().window().maximize();  
     //Go to URL  
     driver.get("http://www.google.com");  
     //Set selenium webdriver get timeout  
 driver.manage().timeouts().implicitlyWait(10,TimeUnit.SECONDS);  
     // Write search String  
 driver.findElement(By.id("gbqfq")).sendKeys("WebDriver");  
     // Check element exists  
  if (driver.findElements(By.id("gbqfb")).size() != 0) {  
       driver.findElement(By.id("gbqfb")).click();  
       System.out.println("element exists");    
     }  
     Thread.sleep(5000);  
     // Browser close   
     driver.close();  
   }  
 }