Ошибка в коде: Exception in thread "main" java.lang.NullPointerException

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
 
import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
 
 
/**
 * Created by master on 23.10.15.
 */
public class ToXLS {
 
 public static void main(String[] args) throws IOException, NullPointerException {
 String a = "ex.xls";
 readFromExcel(a);  //  <---
 }
 public static void readFromExcel(String file) throws FileNotFoundException, IOException {
    HSSFWorkbook myExcelBook = new HSSFWorkbook(new FileInputStream(file));
    HSSFSheet myExcelSheet = myExcelBook.getSheet("1");
    HSSFSheet myExcelSheet2 = myExcelBook.getSheet("2");
 
 HSSFRow row = myExcelSheet.getRow(8); //  <---
 HSSFCell cell00 = row.getCell(0);
 String valCell00 = cell00.getStringCellValue();
 HSSFCell cell01 = row.getCell(1);
 String valCell01 = cell01.getStringCellValue();
 HSSFCell cell02 = row.getCell(2);
 String valCell02 = cell02.getStringCellValue();
 
 HSSFRow row2 = myExcelSheet2.createRow(8);
 HSSFCell cell0 = row2.createCell(0);
 cell0.setCellValue(valCell00);
 HSSFCell cell1 = row2.createCell(1);
 cell1.setCellValue(valCell01);
 HSSFCell cell2 = row2.createCell(2);
 cell2.setCellValue(valCell02);
 
 myExcelBook.write(new FileOutputStream(file));
 
 myExcelBook.close();
 }
}