Null Pointer Exception while using Reflection

Question

I'm following a tutorial for Selenium - Keyword Driven Framework here . I'm not very familiar with the the Reflection API. (I'm a beginner to Java as well)

When I execute my main class, I'm receiving a Null Pointer Exception. I'm not sure what I'm doing wrong. Might be a silly mistake. Please help me understand what I'm missing here. (Also, if someone can guide me where I can learn better about Keyword Driven Framework and the Reflection API from a beginner's standpoint, that would be very helpful.)

DriverScript:

package testdev;

import java.lang.reflect.Method;
import config.ActionKeywords;
import utility.ExcelUtils;

public class DriverScript {

public static ActionKeywords actionKeywords;
public static String sActionKeyword;
public static Method method[];

public DriverScript() throws NoSuchMethodException, SecurityException{
    actionKeywords = new ActionKeywords();
    method = actionKeywords.getClass().getMethods();
}

public static void main(String args[]) throws Exception{

    String sPath = "C://Users//testusr//workspace//src//datasource//datasource.xlsx";
    ExcelUtils.setExcelFile(sPath, "sheet");

    for(int i=1; i<=7; i++){
        sActionKeyword = ExcelUtils.getCellData(i, 3);
        execute_Actions();
    }
}

private static void execute_Actions() throws Exception{

    for(int j=0;j < method.length;j++){
        if(method[j].getName().equals(sActionKeyword)){
            method[j].invoke(actionKeywords);
            break;
        }
    }

}
}

ActionKeywords:

package config;

import java.util.concurrent.TimeUnit;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;

public class ActionKeywords {

public static WebDriver driver;

public static void openbrowser(){
    System.setProperty("webdriver.chrome.driver", "G:\\Usr\\MAC\\Se\\chromedriver.exe");
    driver = new ChromeDriver();
}

public static void navigate(){
    driver.get("URL");
    driver.manage().timeouts().implicitlyWait(5, TimeUnit.SECONDS);
    driver.manage().window().maximize();
}

public static void enter_credentials(){
    driver.findElement(By.id("login-form-username")).sendKeys("username");
    driver.findElement(By.id("login-form-password")).sendKeys("pswd");
}

public static void click_login(){
    driver.findElement(By.id("login")).click();
}

public static void wait_for(){
    driver.manage().timeouts().implicitlyWait(5, TimeUnit.SECONDS);
}

public static void click_logout() throws InterruptedException{
    driver.findElement(By.id("header-details-user-fullname")).click();
    Thread.sleep(30);
    driver.findElement(By.id("log_out")).click();
}

public static void closebrowser(){
    driver.quit();
}

}

ExcelUtils:

package utility;

import java.io.FileInputStream;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class ExcelUtils {

public static XSSFWorkbook ExcelWBook;
public static XSSFSheet ExcelWSheet;
public static XSSFCell Cell;
public static FileInputStream ExcelFile;

public static void setExcelFile (String Path, String SheetName) throws Exception{
    FileInputStream ExcelFile = new FileInputStream(Path);
    ExcelWBook = new XSSFWorkbook(ExcelFile);
    ExcelWSheet = ExcelWBook.getSheetAt(0);
}

public static String getCellData (int rowNum, int colNum) {
    String CellData ="";
    Cell = ExcelWSheet.getRow(rowNum).getCell(colNum);
    CellData= Cell.getStringCellValue();        
    return CellData;
}
}

Exception:

java.lang.NullPointerException
at testdev.DriverScript.execute_Actions(DriverScript.java:37)
at testdev.DriverScript.main(DriverScript.java:28)

Excel sheet :

Answer 1

As said on exception: On line 37;

for (int j = 0; j < method.length; j++) {

method is null. Because you never call constructor to create a new Driverscript Object and so

method = actionKeywords.getClass().getMethods();

line never assign a value to method .

All fields are static but you are trying to assign their values in Constructor.

This is not a good approach but I think above code works as expected for you

public static void main(String args[]) throws Exception{

    String sPath = "C://Users//testusr//workspace//src//datasource//datasource.xlsx";
    ExcelUtils.setExcelFile(sPath, "sheet");

    for(int i=1; i<=7; i++){
        sActionKeyword = ExcelUtils.getCellData(i, 3);
        actionKeywords = new ActionKeywords();
        method = actionKeywords.getClass().getMethods();
        execute_Actions();
    }
}