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  public static void mergeExcelFiles(File file, List<FileInputStream> list) throws IOException {
    HSSFWorkbook book = new HSSFWorkbook();
    HSSFSheet sheet = book.createSheet(file.getName());
    
    for (FileInputStream fin : list) {
      HSSFWorkbook b = new HSSFWorkbook(fin);
      for (int i = 0; i < b.getNumberOfSheets(); i++) {
        copySheets(book, sheet, b.getSheetAt(i));
      }
    }
    
    try {
      writeFile(book, file);
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }
  
  protected static void writeFile(HSSFWorkbook book, File file) throws Exception {
    FileOutputStream out = new FileOutputStream(file);
    book.write(out);
    out.close();
  }
  
  private static void copySheets(HSSFWorkbook newWorkbook, HSSFSheet newSheet, HSSFSheet sheet){     
    copySheets(newWorkbook, newSheet, sheet, true);
  }     

  private static void copySheets(HSSFWorkbook newWorkbook, HSSFSheet newSheet, HSSFSheet sheet, boolean copyStyle){     
    int newRownumber = newSheet.getLastRowNum() + 1;
    int maxColumnNum = 0;     
    Map<Integer, HSSFCellStyle> styleMap = (copyStyle) ? new HashMap<Integer, HSSFCellStyle>() : null;    
    
    for (int i = sheet.getFirstRowNum(); i <= sheet.getLastRowNum(); i++) {     
      HSSFRow srcRow = sheet.getRow(i);     
      HSSFRow destRow = newSheet.createRow(i + newRownumber);     
      if (srcRow != null) {     
        copyRow(newWorkbook, sheet, newSheet, srcRow, destRow, styleMap);     
        if (srcRow.getLastCellNum() > maxColumnNum) {     
            maxColumnNum = srcRow.getLastCellNum();     
        }     
      }     
    }     
    for (int i = 0; i <= maxColumnNum; i++) {     
      newSheet.setColumnWidth(i, sheet.getColumnWidth(i));     
    }     
  }     
  
  public static void copyRow(HSSFWorkbook newWorkbook, HSSFSheet srcSheet, HSSFSheet destSheet, HSSFRow srcRow, HSSFRow destRow, Map<Integer, HSSFCellStyle> styleMap) {     
    destRow.setHeight(srcRow.getHeight());
    for (int j = srcRow.getFirstCellNum(); j <= srcRow.getLastCellNum(); j++) {     
      HSSFCell oldCell = srcRow.getCell(j);
      HSSFCell newCell = destRow.getCell(j);
      if (oldCell != null) {     
        if (newCell == null) {     
          newCell = destRow.createCell(j);     
        }     
        copyCell(newWorkbook, oldCell, newCell, styleMap);
      }     
    }                
  }
  
  public static void copyCell(HSSFWorkbook newWorkbook, HSSFCell oldCell, HSSFCell newCell, Map<Integer, HSSFCellStyle> styleMap) {      
    if(styleMap != null) {     
      int stHashCode = oldCell.getCellStyle().hashCode();     
      HSSFCellStyle newCellStyle = styleMap.get(stHashCode);     
      if(newCellStyle == null){     
        newCellStyle = newWorkbook.createCellStyle();     
        newCellStyle.cloneStyleFrom(oldCell.getCellStyle());     
        styleMap.put(stHashCode, newCellStyle);     
      }     
      newCell.setCellStyle(newCellStyle);   
    }     
    switch(oldCell.getCellType()) {     
      case HSSFCell.CELL_TYPE_STRING:     
        newCell.setCellValue(oldCell.getRichStringCellValue());     
        break;     
      case HSSFCell.CELL_TYPE_NUMERIC:     
        newCell.setCellValue(oldCell.getNumericCellValue());     
        break;     
      case HSSFCell.CELL_TYPE_BLANK:     
        newCell.setCellType(HSSFCell.CELL_TYPE_BLANK);     
        break;     
      case HSSFCell.CELL_TYPE_BOOLEAN:     
        newCell.setCellValue(oldCell.getBooleanCellValue());     
        break;     
      case HSSFCell.CELL_TYPE_ERROR:     
        newCell.setCellErrorValue(oldCell.getErrorCellValue());     
        break;     
      case HSSFCell.CELL_TYPE_FORMULA:     
        newCell.setCellFormula(oldCell.getCellFormula());     
        break;     
      default:     
        break;     
    }
  }