getWindowHandle() throws error message "Nullpointerexception" - selenium

Question

this is a simple selenium function that is trying to get a windowhandle.
right at that statement it throws" Nullpointerexception"
import static org.junit.Assert.*;
import java.util.concurrent.TimeUnit;
import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
public class WindowHandles {
WebDriver achromeDriver;
String abaseUrl;
public void setUp() throws Exception {
abaseUrl = "http://letskodeit.teachable.com/pages/practice";
System.setProperty("webdriver.chrome.driver", "C:\\Selenium\\ChromeDirver\\chromedriver.exe");
achromeDriver = new ChromeDriver();
achromeDriver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
achromeDriver.manage().window().maximize();;
System.out.println("setup completed");
}
#Test
public void test() {
try{
String aparentwindowHandle = achromeDriver.getWindowHandle();
System.out.println("the parent window handle is "+ aparentwindowHandle);
WebElement aopenwindowelementbutton = achromeDriver.findElement(By.id("openwindow"));
aopenwindowelementbutton.click();
String achildwindowhandle = achromeDriver.getWindowHandle();
System.out.println("the child window handle is: " + achildwindowhandle);
}catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

Answer 1

A bit more details about your usecase and your observation would have helped us to debug the issue in a better way. However, it seems as you are using the junit framework and in-absence of any of the annotations the setUp() method is never executed.
As the test() method is annotated with #Test the program reaches there with achromeDriver as Null
Solution
A quick solution would be to add #Before annotation to setUp() method as follows:
#Before
public void setUp() throws Exception {
abaseUrl = "http://letskodeit.teachable.com/pages/practice";
System.setProperty("webdriver.chrome.driver", "C:\\Selenium\\ChromeDirver\\chromedriver.exe");
achromeDriver = new ChromeDriver();
achromeDriver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
achromeDriver.manage().window().maximize();;
System.out.println("setup completed");
}