sheet gives me null pointer apache poi

I want to create a file .xls but when I set a value it gives me null pointer. this is my code :

(the file xls is empty at start and I need to create two sheet from the code):

Workbook wb = new HSSFWorkbook();
       Sheet general=wb.createSheet("General"); 
    
    //after this line it gives me null point
                Row row = general.getRow(0);    
                Cell cell = row.getCell(1);   

It seems that "general" is null.Anyone can help me?

>Solution :

getRow(0) throws Exception because row-0 does not exist.
you need to create the row in the first place :

Row row = general.createRow(0);