get Response - IllegalStateException exception

import java.io.IOException;

import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.fluent.Request;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;

/**
*
*/

/**
* @author Shamal
*
*/
public class findingResponse {

/**
* @param args
*/
public static void main(String[] args) {
WebDriver driver=new FirefoxDriver();
boolean response=getResponseCode("http://gmail.com");
System.out.println("Response : " + response);
driver.get("http://www.gmail.com");


/*driver.findElement(By.id("Email")).sendKeys("XXXXx");
String data=driver.findElement(By.id("Email")).getText();
System.out.println(data);
data=driver.findElement(By.id("Email")).getAttribute("value");
System.out.println("value : " + data);
data=driver.findElement(By.id("Email")).getAttribute("placeholder");
System.out.println("placeholder : " + data);
data=driver.findElement(By.id("signIn")).getAttribute("value");
System.out.println("Button Text : " + data);
data=driver.findElement(By.xpath("//div[@class='banner']/h1")).getText();
System.out.println("Normal text: " + data);
*/
}
public static boolean getResponseCode(String url)
{
int resp_code=0;
try {
resp_code = Request.Get("").execute().returnResponse().getStatusLine().getStatusCode();
System.out.println("Response code for url: " +url + " is " + resp_code);

} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(resp_code==200)
return true;
else
return false;

}
}
here i am getting exception:
Exception in thread "main" java.lang.IllegalStateException: Target host is null
at org.apache.http.util.Asserts.notNull(Asserts.java:52)
at org.apache.http.impl.conn.DefaultHttpRoutePlanner.determineRoute(DefaultHttpRoutePlanner.java:98)
at org.apache.http.impl.client.DefaultRequestDirector.determineRoute(DefaultRequestDirector.java:762)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:381)
at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:882)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:107)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:55)
at org.apache.http.client.fluent.Request.execute(Request.java:145)
at findingResponse.getResponseCode(findingResponse.java:46)
at findingResponse.main(findingResponse.java:24)