NullPointerException generating 0 byte files

[Meike Reichle \(RZ\)]

Hi everyone,

I am rather new to POI, but I am planing to use it for a project,
so I decided to first test it a bit before actually starting using it
in a big scale.
But unfortunatelly I just don't get it to work properly. 
What I wanted to do is to open an existing file, add some values 
and write that in a new file. Opening seems to work, but then 
I am doing something wrong and I can't  really figure out what it is. 
The class compiles without errors, but when I try to execute it, 
it throws three NullPointerExceptions and generates a new file with 
the size of 0 bytes. 

It's probably a rather dumb newbie mistake I did. But since I am still 
trying to understand the concept of  POI I'd be really glad if someone 
had a hint or some enlightening words for me.

Thanks in advance,
Meike


Here's my complete testing class: 


import java.io.*;
import org.apache.poi.poifs.filesystem.*;
import org.apache.poi.hssf.dev.*;
import org.apache.poi.hssf.eventmodel.*;
import org.apache.poi.hssf.model.*;
import org.apache.poi.hssf.record.*;
import org.apache.poi.hssf.usermodel.*;
import org.apache.poi.hssf.util.*;

public class ExcelInterface 
{
     
    //opening an existing file
     public static HSSFWorkbook openFile()
     {
      try
      {
           FileInputStream in = new FileInputStream(Pfade.excel);
           POIFSFileSystem fs = new POIFSFileSystem(in);
           HSSFWorkbook wb = new HSSFWorkbook(fs);
           return wb;
      }
      catch(Exception e)
      {
           System.out.println(e);
      } 
      return null;
     }
 

    //write in some values
     public static HSSFWorkbook fill()
     {
      try 
      {
           HSSFWorkbook wb = openFile();
           HSSFSheet sheet = wb.getSheetAt(1);
           HSSFRow row = sheet.getRow(0);
           HSSFCell cell1 = row.getCell((short)1);
           HSSFCell cell2 = row.getCell((short)2);
   
           cell1.setCellType(HSSFCell.CELL_TYPE_NUMERIC);
           cell2.setCellType(HSSFCell.CELL_TYPE_STRING);
           cell1.setCellValue(15);
           cell2.setCellValue("test :-)");
      }
      catch(Exception e)
      {
           System.out.println(e);
      } 
      return null;
     }
 


    //Save it to a new file
     public static void closeFile()
     {
      try
      {   
           HSSFWorkbook wb = fill();
           FileOutputStream out = new FileOutputStream(Pfade.excel2);
           wb.write(out);
           out.close();
      }
      catch(Exception e)
      {
           System.out.println(e);
      }
     }
 

 public static void main(String args[])
 {  
  openFile();
  fill();
  closeFile();
 }
 
}//end of class


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