Selenium:How to upload a file using sendkeys() method

package files;

import java.util.concurrent.TimeUnit;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

public class FileUpload {

    WebDriver driver;
     @Test
      public void dragdrop() throws InterruptedException {
         driver.get("https://www.sendspace.com/");
        driver.manage().window().maximize();
        Thread.sleep(2000);       
        driver.findElement(By.id("upload_file")).sendKeys("C:\\Users\\Ramesh\\Desktop\\blog.txt");
         Thread.sleep(6000);
     }
   
     @BeforeClass
      public void beforeClass() {
          System.setProperty("webdriver.firefox.bin",
                    "C:\\Users\\Ramesh\\AppData\\Local\\Mozilla Firefox\\firefox.exe");
          driver=new FirefoxDriver();
          driver.manage().window().maximize();
          driver.manage().timeouts().implicitlyWait(30,TimeUnit.SECONDS);
         
      }

      @AfterClass
      public void afterClass() {
          driver.quit();
         
      }
   
}