捕获的异常是：java.lang.NullPointerException

Question

异常捕获的是：java.lang.NullPointerException FAILED：在PriceLine.com.ApplicationUtilities.returnWebElement（ApplicationUtilities.java:40）上的SearchFlightAndCars java.lang.NullPointerException，在priceLine.com.SeleniumTest.SearchFlightAndCars上的priceLine.com.MainSetUp.Login（MainSetUp.java:45）

` ApplicationUtitlies.java

package priceLine.com;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;

public class ApplicationUtilities
{
  WebElement myElement;
  WebDriver driver;

public ApplicationUtilities(WebDriver driver) {
    this.driver = driver;
}

public WebElement returnWebElement(String propType,String propValue)
{
try
{
if(propType.equals("id"))
    myElement = driver.findElement(By.id(propValue));
else if(propType.equals("name"))
    myElement = driver.findElement(By.name(propValue));
else if(propType.equals("className"))
    myElement = driver.findElement(By.className(propValue));
else if(propType.equals("xpath"))
    myElement = driver.findElement(By.xpath(propValue));
else if(propType.equals("cssSelector"))
    myElement = driver.findElement(By.cssSelector(propValue));
else if(propType.equals("linkText"))
    myElement = driver.findElement(By.linkText(propValue));
else if(propType.equals("partialLinkText"))
    myElement = driver.findElement(By.partialLinkText(propValue));
else if(propType.equals("tagName"))
    myElement = driver.findElement(By.tagName(propValue));
}
    catch(Exception e)
{
        System.out.println("exception caught is :"+e);
}
if(myElement.isEnabled())
    return myElement;
else
    System.out.println("element cannot be found");
    return null;    
}

}`

` ReadProperties.java

package priceLine.com;

import java.io.FileInputStream;
import java.util.Properties;

public class ReadProperties {
static Properties prop;
static FileInputStream file;
public static String readValue(String key)
{
try {
file = new    FileInputStream("F:\\SeleniumLearning\\SeleniumPractice\\TestData\\Data.properties");
        prop = new Properties();
        prop.load(file);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return prop.getProperty(key);
    }
 }`

` MainSetUp.java

package priceLine.com;

import java.util.concurrent.TimeUnit;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.ie.InternetExplorerDriver;
import priceLine.com.ReadProperties;

public class MainSetUp  {
WebElement myElement;
public WebDriver driver;
ApplicationUtilities myUtil = new ApplicationUtilities(driver);
public WebDriver setUp()
{
    String browserName = ReadProperties.readValue("browser");

    if(browserName.equals("chrome"))
    {
        System.setProperty("webdriver.chrome.driver",   "F:\\SeleniumLearning\\SeleniumPractice\\Lib\\chromedriver.exe");
        driver = new ChromeDriver();
    }
    else if(browserName.equals("firefox"))
    {
        System.setProperty("webdriver.chrome.driver", "F:\\SeleniumLearning\\SeleniumPractice\\Lib\\geckodriver.exe");
        driver = new FirefoxDriver();
    }
    else if(browserName.equals("InternetExplorer")) 
    {
        System.setProperty("webdriver.ie.driver", "F:\\SeleniumLearning\\SeleniumPractice\\Lib\\IEDriverServer.exe");
        driver = new InternetExplorerDriver();  
    }
    driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
    return driver;
}
public void URL()
{
    driver.get(ReadProperties.readValue("url"));
}
//  ************************** Website Operations ********************
public void Login()
{
    System.out.println("Should Click on Sign In");
    myUtil.returnWebElement("cssSelector", "button[type='button']").click();
    myUtil.returnWebElement("name", "lname").sendKeys(ReadProperties.readValue("username"));    
    myUtil.returnWebElement("cssSelector", ".register__form-field-password").sendKeys(ReadProperties.readValue("password"));
    myUtil.returnWebElement("xpath", "//button[@id='button-sign-in']").click();
}
}

`

` SeleniumTest.java

package priceLine.com;

import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;

public class SeleniumTest {

MainSetUp setUp = new MainSetUp();


@BeforeTest
public void SetBrowserAndUrl()
{
setUp.setUp();
//  driver.get(ReadProperties.readValue("url"));
setUp.URL();    


}
@Test
public void SearchFlightAndCars()
{   
setUp.Login();
}
} `