Null pointer exception when calling a action class of page object model

TestConfused.java:
public class TestCase extends TestBase 
{
homeDetails homePage;
CarActions carsPage;
Map<Object, Object> map= new HashMap<Object, Object>();
@BeforeMethod
public void startdriver()   
     {

        startapplication();
        object= new ExcelReader();
        driver.get(url);
        driver.manage().deleteAllCookies();
        driver.manage().timeouts().implicitlyWait(50, TimeUnit.SECONDS);
        utility= new Utility();

    }
   
    }

    @Test(dataProvider= "data")
    public void CarTest(Map<Object, Object> car ) throws IOException, Exception {
         carsPage= new CarActions();
         System.out.println(car);
         carsPage.makeAndModel(car);
}
    @DataProvider(name = "data")  
    public static Object[][] CarTestData() throws IOException, Exception 
  {
        object= new ExcelReader();
        return object.getExcelData("Sheet1", fileDir);
  }
}

**CarAction.java:**

public class CarActions extends TestBase {
    WebDriver driver;

    CarPage car_pg = PageFactory.initElements(driver, CarPage.class);

public void makeAndModel(Map<Object, Object> map) throws IOException, Exception {
    
        String registerNumber= map.get("RegisterNo").toString();
        utility.elementCheck(car_pg.registerNo);
        car_pg.registerNo.click();
        car_pg.registerNo.sendKeys(registerNumber);
        car_pg.findVehicle.click();
    }
**carPage.java:**
    public class CarPage {

    @FindBy(how = How.XPATH, using = "//input[@id='RegistrationNumber']" )
    public WebElement registerNo;

ExcelReader.java: 

public class ExcelReader extends TestBase
 {
<pre>public  Object[][] getExcelData( String SheetName , String fileDir ) throws IOException {
    
       File srcFile = new File(fileDir);
       FileInputStream fis = new FileInputStream(srcFile);
       XSSFWorkbook wb = new XSSFWorkbook(fis);
       XSSFSheet sheet= wb.getSheet(SheetName);
       wb.close();
       int lastRowNum = sheet.getLastRowNum() ;
        int lastCellNum = sheet.getRow(0).getLastCellNum();
    
        Object[][] obj = new Object[lastRowNum][1];

        for (int i = 0; i < lastRowNum; i++) {
          Map<Object, Object> datamap = new HashMap<Object, Object>();
          for (int j = 0; j < lastCellNum; j++) {
        
            datamap.put(sheet.getRow(0).getCell(j).toString(), 
  sheet.getRow(i+1).getCell(j).toString());
          }
          obj[i][0] = datamap;

        }
        return  obj;
      }
}
**TestBase.java**

public class TestBase {

    public static WebDriver driver;
    public static Actions action;
    public static ExcelReader object;
    public static Utility utility;
    public String url= "https";
    protected static String fileDir= "\\InputHMap.xlsx";
    static String browserName;
    static String driverPath;
    public static Properties prop;
    public static WebDriverWait wait;

    public static void startapplication(){
        String browser="CHROME";
        if(browser.equals("CHROME"))
        {
            System.setProperty("Webdriver.chrome.driver","./chromedriver.exe");
            driver = new ChromeDriver();
        }
        else if(browser.equals("IE"))
        {
            System.setProperty("Webdriver.ie.driver","./geckodriver.exe");
            driver = new InternetExplorerDriver();
        }
         else
        {
            System.out.println("we do not support this browser");
        }
    
            driver.manage().window().maximize();
    }
}
**utility.java**
public class Utility {
    protected WebDriver driver = null;
    public void enterText(WebElement element, String value) {
        if(null != value)
        {
            //element.clear();
            element.sendKeys(value);
        }
    }



  public void elementCheck(WebElement element) throws IOException {

    WebDriverWait wait=new WebDriverWait(driver,20);
        wait.until(ExpectedConditions.visibilityOf(element));           
    }   
}
My problem is whenever the carpage.makeandmodel() is invoked in the @Test of TestConfused.java, a 
null pointer exception is encountered.

I am trying my hands on Selenium test automation using TestNG as the test framework. For this, I have 
used a Page Object pattern to model each of the pages of the website that I am writing the test for.