Why I am getting Data Provider MisMatch error when I try to read from excel file?

I am trying to do data driven testing and I am not able to figure it out why I am getting data mismatch. I am trying to automate just usernames and that is in form of string. Can you please review my code and tell me what I am doing wrong?
Below are two files. one is my main method file and one is my excel config file. I have also attached screenshot of my error. Any help would be appreciated. Thank you.

File1:

`

package loginAdmin;
import java.util.concurrent.TimeUnit;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
public class PersonateUser {
@Test(dataProvider="testdata") 
public void login(String username) throws InterruptedException
{
System.setProperty("webdriver.chrome.driver",
C:\\Users\\abc\\Downloads\\chromedriver_win32\\chromedriver.exe");
WebDriver driver = new ChromeDriver();
driver.manage().deleteAllCookies();
driver.manage().window().maximize();
driver.manage().timeouts().implicitlyWait(200, TimeUnit.SECONDS);
driver.manage().timeouts().pageLoadTimeout(200, TimeUnit.SECONDS);
driver.get("www.abc.com/AdminHome.aspx");
driver.findElement(By.id("M_layout_content_PCDZ_MW2NO7V_ctl00_webInputForm_txtLoginName")).
sendKeys("admin");   
driver.findElement(By.id("M_layout_content_PCDZ_MW2NO7V_ctl00_webInputForm_txtPassword")).
sendKeys("Password");    
driver.findElement(By.id("M_layout_content_PCDZ_MW2NO7V_ctl00_webInputForm_cmdContinue")).
click();
driver.findElement(By.id("M_layout_content_PCDZ_M5QH8YG_ctl00_lblUserName")).
click();
driver.findElement(By.id("M_layout_content_PCDZ_M5QH8YG_ctl00_txtUserName")).
sendKeys(username);
driver.findElement(By.id("M_layout_content_PCDZ_M5QH8YG_ctl00_btnSearch")).click();
driver.findElement(By.id("M_layout_content_PCDZ_M5QH8YG_ctl00_resultsGrid_ctl02_LogInAsUser")).
click(); 			
System.out.println("User is able to login successfully");
driver.findElement(By.xpath("/html/body/form/div[3]/div[3]/div[1]/div[1]/div/div[5]/ul/li[6]/a")).
click();	      
@DataProvider(name="testdata")
public Object[][] TestDataFeed()
{
ReadExcelFile config = new 
ReadExcelFile("C:\\Users\\abc\\eclipseworkspace\\Login\\testdata\\testdata.xlsx");
int rows = config.getRowCount(0);
Object[][] credentials = new Object[rows][2];
for(int i = 0; i < rows; i++)
{
credentials[i][0] = config.getData(0, i, 0);
}
return credentials;
}

}

`

File 2:

` package loginAdmin;
import java.io.File;
import java.io.FileInputStream;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class ReadExcelFile
{
XSSFWorkbook wb;
XSSFSheet sheet;	 
public ReadExcelFile(String excelPath)
{
try
{ 
File src = new File(excelPath);
FileInputStream fis = new FileInputStream(src);
wb =new XSSFWorkbook(fis);
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
}
public String getData(int sheetnumber, int row, int column)
{
sheet= wb.getSheetAt(sheetnumber);
String data = sheet.getRow(row).getCell(column).getStringCellValue();
return data;
}
public int getRowCount(int sheetIndex)
{
int row = wb.getSheetAt(sheetIndex).getLastRowNum();
row = row + 1;
return row;
}
}
`

Error Screenshot:

Excel File:

You are declaring Object[][] credentials = new Object[rows][2]; but you fill only one column keeping other column empty (null). Hence the dimension of your array does not match the number of arguments your method accepts.

Fix it with changing that line to:

Object[][] credentials = new Object[rows][1];