How to insert text in text field of model window using selenium webdriver ?

We have to navigateto Alert or Confirmation windows

driver.switchTo().alert();                                                   

To click on "OK"  or "Cancel" on Alertor Confirmation 

driver.switchTo().alert().accept();—ToclickOK                   

driver.switchTo().alert().dismiss();—ToclickCancel          

@Test
public void Entertext()throws Exception

{
driver.get("http://seleniumsubbu.blogspot.in/");
Thread.sleep(5000);
driver.findElement(By.xpath("//*[@id='node-223']/div/div[1]/div/div/button")).click();
Alert alert = driver.switchTo().alert();
alert.sendKeys("The value that you wish to enter");
alert.accept();
}