如何将对象传递给函数

Question

是否可以将对象传递给函数？执行以下命令时，它说它无法将方法createRow传递给空对象

import org.apache.poi.ss.usermodel.*
import org.apache.poi.hssf.usermodel.*
import org.apache.poi.xssf.usermodel.*
import org.apache.poi.ss.util.*
import org.apache.poi.ss.usermodel.*
//import java.io.*

def getCellFromAddress(Sheet sheet, colNumber, rowNumber)
{
Row row = sheet.createRow(rowNumber);

Cell cell = row.createCell(colNumber);
return cell;
}

xlFileAddress = 'file.xlsx';
Workbook wb = WorkbookFactory.create(new FileInputStream(xlFileAddress));
Sheet sheet = wb.getSheet("Sheet1");

// Create a cell and put a value in it.
getCellFromAddress(sheet, "H9").setCellValue("test value");