title: Null Pointer Exception while running code using TestNG
body: <p>I am trying to automate a Login and Logout Scenario in TestNG and passing the browser as parameter from XML on the basis of which chromedriver() instance will be created and the code will run.I have two classes TestRunner and Login where login method gets data (username and password) TestRunner and data is fetched from excel.Exception e is getting null value as I found out while debugging. Any way to fix it?</p>
  
  <pre><code>FAILED: Registration_data("ashwin@gmail.com", "ashwin123")
  java.lang.NullPointerException
  at com.DataDriven.Login.login(Login.java:68)
  at com.DataDriven.TestRunner.Registration_data(TestRunner.java:28)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at   sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at   sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:483)
  at   org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
  at org.testng.internal.Invoker.invokeMethod(Invoker.java:714)
  at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
  at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
  at     org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:12)
  at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
  at org.testng.TestRunner.privateRun(TestRunner.java:767)
  at org.testng.TestRunner.run(TestRunner.java:617)
  at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
  at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
  at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
  at org.testng.SuiteRunner.run(SuiteRunner.java:240)
  at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
  at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
  at org.testng.TestNG.runSuitesSequentially(TestNG.java:1224)
  at org.testng.TestNG.runSuitesLocally(TestNG.java:1149)
  at org.testng.TestNG.run(TestNG.java:1057)
  at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
  at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
  </code></pre>
  
  <hr>
  
  <pre><code>    package com.DataDriven;
      import java.util.concurrent.TimeUnit;
      import org.openqa.selenium.By;
      import org.openqa.selenium.WebDriver;
      import org.openqa.selenium.firefox.FirefoxDriver;
      public class TestRunner {
  
      @Test(dataProvider = "Authentication")
      public static void Registration_data(String sUserName, String sPassword)
          throws Exception {
  
      Login lp = new Login();
      lp.login(sUserName, sPassword);
      }
  
      @DataProvider
      public Object[][] Authentication() throws Exception {
  
      Object[][] testObjArray = ReadData.getTableArray(
              "F:\\Automation\\DataDrivenPractice\\DataFiles\\DataFile.xlsx",
              "Sheet1");
  
      return (testObjArray);  }  }
  </code></pre>
  
  <hr>
  
  <pre><code>    package com.DataDriven;
  
      import java.io.File;
  
      import org.apache.commons.io.FileUtils;
      import org.openqa.selenium.By;
      import org.openqa.selenium.OutputType;
      import org.openqa.selenium.TakesScreenshot;
      import org.openqa.selenium.WebDriver;
      import org.openqa.selenium.chrome.ChromeDriver;
  
      public class Login {
       WebDriver driver = null;
  
       @Parameters("browser")
       @BeforeClass
      // Passing Browser parameter from TestNG xml
      public void beforeTest(String browser) {
  
      // If the browser is Firefox, then do this
  
      if (browser.equalsIgnoreCase("firefox")) {
  
          driver = new FirefoxDriver();
  
          // If browser is IE, then do this
  
        } else if (browser.equalsIgnoreCase("chrome")) {
  
          // Here I am setting up the path for my IEDriver
  
          driver = new ChromeDriver(); } }
  
       public void login(String username, String password) {
          try {
          driver.get("https://www.facebook.com/");
  
          driver.findElement(By.id("email")).sendKeys(username);
          driver.findElement(By.id("pass")).sendKeys(password);
          driver.findElement(By.id("loginbutton")).click();
          driver.findElement(By.linkText("Log Out")).click();
           }
  
         catch (Exception e) {
          File srcfile = ((TakesScreenshot) driver)
                  .getScreenshotAs(OutputType.FILE);
  
          try {
              FileUtils.copyFile(srcfile, new File(
                      "F:\\Automation\\Screenshots\\Login.jpg"));
          } catch (Exception e1) {
              e1.printStackTrace();
          }   }  }}
  </code></pre>
  
  <hr>
  
  <pre><code>        &lt;?xml version="1.0" encoding="UTF-8"?&gt;
          &lt;!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd"&gt;
          &lt;suite name="Suite" parallel="none"&gt;
          &lt;test name="FirefoxTest"&gt;
           &lt;parameter name="browser" value="chrome" /&gt;
           &lt;classes&gt;
           &lt;class name="com.DataDriven.TestRunner" /&gt;
           &lt;class name="com.DataDriven.Login" /&gt; 
           &lt;/classes&gt;
           &lt;/test&gt;
           &lt;/suite&gt;
  </code></pre>