Получение ошибки "Невозможно прочитать весь заголовок" при создании файла через apache POI

Question

I am using Java and POI 3.7 and I want to perform following in xlWrite() function-
1. Check the file. If it doesn't exist create a new one.
   If file exists, delete it and create a new one. 
   (DO I have to delete it or if it exists already my new content will overwrite it?) 
2. Once check in 1. is completed, create a new sheet in the workbook if it doesn't exists. 

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Вопросы:

1. В функции записи XL я получаю выше исключение, если я раскомментирую часть создания файла. В остальном работает нормально. Что я должен изменить в своей программе, чтобы достичь того, чего я хочу?

2. Я не уверен. Должен ли я использовать HSSF или XSSF? И это хорошо. Сейчас я должен сохранить свой Excel как.xls для запуска программы. Он не принимает.xlsx. Что я должен делать?

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Я создал класс xl для выполнения операций чтения и записи в Excel, и я буду вызывать эти функции из своего сценария. Программа, которую я написал, как указано ниже, но я получаю исключение -

package lampsplus.utilities;


import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

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;


public class XLOperations{

    //variables declaration
    private int i,j,k;
    private int xRows, xCols;
    private String xlData[][];
    private HSSFRow row;
    private HSSFCell cell;
    private File xlFile;
    private FileInputStream inStream;
    private FileOutputStream outStream;
    private HSSFWorkbook workbook;
    private HSSFSheet sheet;

    /**
     * This method returns XL read from file.
     *
     * @return String[][]  - two dimensional array of read data. 
     */ 
    public String[][] getXLData()
    {
        return xlData;
    }


    /**
     * Class constructor to initialize variables.
     *
     */ 
     public void XLOperations()
     {
         System.out.println("initializing constructor dboperations:");
         this.xlData= null;
         this.row = null;
         this.cell = null;
         this.xlFile = null;
         this.inStream = null;
         this.outStream = null;
         this.workbook = null;
         this.sheet = null;
     }



    /**
     * This method is for reading a excel file in two dimensional array. 
     *
     * @param String - filePath - Path of the file from where to read the information.
     * @param String - sheetName -Name of the sheet to read from file. 
     * @return void
     * @throws Exception - An unexpected exception
     */ 
    public void xlRead(String filePath,String sheetName) throws Exception
    {
        File file = new File(filePath);
        filePath= file.getAbsolutePath(); 

        xlFile = new File(filePath);
        inStream = new FileInputStream(xlFile);
        workbook = new HSSFWorkbook(inStream);
        sheet = workbook.getSheet(sheetName);  
        xRows = sheet.getLastRowNum()+1  ;
        xCols = sheet.getRow(0).getLastCellNum();
        xlData = new String[xRows][xCols];

        for(i=0;i<xRows;i++)
        {
            row = sheet.getRow(i);
            for(j=0;j<xCols;j++)
            {
                cell = row.getCell(j);
                String value = cellToString(cell);
                xlData[i][j] = value;
            } 
        } 
    }    


    /**
     * This method is for writing a writing a excel sheet into a file. 
     *
     * @param String - filePath 
     * @param String - sheetname 
     * @param string - two dimensional array to write in the file
     * @return void
     * @throws Exception - An unexpected exception
     */ 
    public void xlWrite(String filePath,String sheetName,String data[][]) throws Exception
    {
        File file = new File(filePath);
        filePath= file.getAbsolutePath(); 


        xlFile = new File(filePath);

    /*   if(!xlFile.exists())
         {
                System.out.println("Created file");
             xlFile.createNewFile();
         }   
         */

        inStream = new FileInputStream(xlFile);
        workbook = new HSSFWorkbook(inStream);
        k = workbook.getSheetIndex(sheetName);
        if(k!=-1)
        {   
            workbook.removeSheetAt(k);
        }   
        HSSFSheet sheet = workbook.createSheet(sheetName);
        FileOutputStream fOut = new FileOutputStream(xlFile);


        xRows = data.length;
        xCols = data[0].length;
        for(i =0;i<xRows;i++)
        {
            row = sheet.createRow(i);
            for(j=0;j<xCols;j++)
            {
                cell = row.createCell(j);
                cell.setCellType(HSSFCell.CELL_TYPE_STRING);
                cell.setCellValue(data[i][j]);
            } 

        } 
        workbook.write(fOut);
        fOut.flush();
        fOut.close();
    }      

    public String cellToString(HSSFCell cell)
    {
        int type = cell.getCellType();
        Object result;
        switch(type)
        {
        case HSSFCell.CELL_TYPE_NUMERIC: //0
            result = cell.getNumericCellValue();
                break;
        case HSSFCell.CELL_TYPE_STRING://1
            result = cell.getStringCellValue();
                break;
        case HSSFCell.CELL_TYPE_FORMULA://2
            throw new RuntimeException("Java can't evaluate formulas");
        case HSSFCell.CELL_TYPE_BLANK://3
            result = "";
                break;
        case HSSFCell.CELL_TYPE_BOOLEAN://4
            result = cell.getBooleanCellValue();
                break;
        case HSSFCell.CELL_TYPE_ERROR://5
            throw new RuntimeException("This cell has an error");
        default:
            throw new RuntimeException("We don't support this cell type:" + type);
        } 
        return result.toString();
    } 

}

Исключение, которое я получаю

java.io.IOException: Unable to read entire header; 0 bytes read; expected 32 bytes
    at org.apache.poi.poifs.storage.HeaderBlockReader.alertShortRead(HeaderBlockReader.java:176)
    at org.apache.poi.poifs.storage.HeaderBlockReader.<init>(HeaderBlockReader.java:103)
    at org.apache.poi.poifs.filesystem.POIFSFileSystem.<init>(POIFSFileSystem.java:153)
    at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:305)
    at org.apache.poi.hssf.usermodel.HSSFWorkbook.<init>(HSSFWorkbook.java:286)
    at tryIng.xlWrite(tryIng.java:74)
    at tryIng.main(tryIng.java:49)