WebDriver driver;
    WebDriverWait wait;
    LoginScreen loginExcel;
    @BeforeClass
            public void beforeClass ()
            {
                System.setProperty("webdriver.chrome.driver", "D:\Madiha\Softwares\Mobile Automation\chromedriver.exe");
                driver=new ChromeDriver();
                driver.manage().window().maximize();
                driver.get("http://10.7.1.180/views/index.html#/login");
                System.out.println(driver.getTitle());
            }

      @Test
            public void LoginWithValidWebExcelEmailAndPass() throws IOException, BiffException  {
     WebElement username= driver.findElement(By.xpath("/html/body/div/div[2]/div[2]/div[1]/div[1]/form/div[1]/input"));
            username.sendKeys("magri");//("/html/body/div/div[2]/div[2]/div[1]/div[1]/form/div[1]/input"));
            WebElement password =  driver.findElement(By.xpath("/html/body/div/div[2]/div[2]/div[1]/div[1]/form/div[2]/input"));
            password.sendKeys("magri");//xpath("/html/body/div/div[2]/div[2]/div[1]/div[1]/form/div[2]/input"));
            WebElement btn = driver.findElement(By.xpath("/html/body/div/div[2]/div[2]/div[1]/div[1]/form/div[5]/button"));
            btn.click();
      }
    }

package SourceSmartWeb;

import java.io.IOException;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

import jxl.JXLException;
import objectRepoWeb.LogoutScreen;

public class LogoutWeb extends LoginWeb{
    WebDriver driver;

    @BeforeClass
            public void beforeClass (){
                System.setProperty("webdriver.chrome.driver", "D:\Madiha\Softwares\Mobile Automation\chromedriver.exe");
                driver=new ChromeDriver();
                driver.get("http://10.7.1.180/views/index.html#/login");
                System.out.println(driver.getTitle());

            }

      @Test (dependsOnMethods = {"LoginWithValidWebExcelEmailAndPass"} )
      public void Logout() throws JXLException, IOException, InterruptedException {
            LogoutScreen logout =  new LogoutScreen(driver);
            logout.ClickToLogout();
      }
}

FAILED: LoginWithValidWebExcelEmailAndPass
java.lang.NullPointerException
    at SourceSmartWeb.LoginWeb.LoginWithValidWebExcelEmailAndPass(LoginWeb.java:63)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:108)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:661)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:869)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1193)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:126)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
    at org.testng.TestRunner.privateRun(TestRunner.java:744)
    at org.testng.TestRunner.run(TestRunner.java:602)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:380)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:375)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:340)
    at org.testng.SuiteRunner.run(SuiteRunner.java:289)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1301)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1226)
    at org.testng.TestNG.runSuites(TestNG.java:1144)
    at org.testng.TestNG.run(TestNG.java:1115)
    at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:132)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:230)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:76)