Program: 126340
Project: 126340
Buggy source:
private void init() throws BiffException, IOException {
  if (!isXlsx) {
    WorkbookSettings worksetting=new WorkbookSettings();
    worksetting.setCellValidationDisabled(true);
    worksetting.setSuppressWarnings(true);
    workbook=Workbook.getWorkbook(new File(excelPath),worksetting);
  }
 else {
    File file=new File(excelPath);
    OPCPackage clone=null;
    try {
      FileInputStream in=new FileInputStream(file);
      OPCPackage open=OPCPackage.open(in);
      clone=PackageHelper.clone(open,PackageHelper.createTempFile());
      open.close();
    }
 catch (    InvalidFormatException e) {
      e.printStackTrace();
    }
catch (    OpenXML4JException e) {
      e.printStackTrace();
    }
    if (clone != null) {
      List<String> sheetlist=new ArrayList<String>();
      if (isXlsx && (EVENT_MODE).equals(generationMode)) {
        try {
          XSSFReader xssfReader=new XSSFReader(clone);
          XSSFReader.SheetIterator sheets=(XSSFReader.SheetIterator)xssfReader.getSheetsData();
          while (sheets.hasNext()) {
            sheets.next();
            String sheetName=sheets.getSheetName();
            sheetlist.add(sheetName);
          }
        }
 catch (        OpenXML4JException e) {
          CommonExceptionHandler.process(e);
        }
      }
 else {
        xwb=new XSSFWorkbook(clone);
        for (        XSSFSheet sheet : xwb) {
          sheetlist.add(sheet.getSheetName());
        }
      }
      sheetNamesForXlsx=new String[sheetlist.size()];
      for (int i=0; i < sheetlist.size(); i++) {
        sheetNamesForXlsx[i]=sheetlist.get(i);
      }
      sheetlist.clear();
    }
  }
}

Fixed version (ground truth):
private void init() throws BiffException, IOException {
  if (!isXlsx) {
    WorkbookSettings worksetting=new WorkbookSettings();
    worksetting.setCellValidationDisabled(true);
    worksetting.setSuppressWarnings(true);
    workbook=Workbook.getWorkbook(new File(excelPath),worksetting);
  }
 else {
    File file=new File(excelPath);
    OPCPackage clone=null;
    try {
      FileInputStream in=new FileInputStream(file);
      OPCPackage open=OPCPackage.open(in);
      clone=PackageHelper.clone(open,createTempFile());
      open.close();
    }
 catch (    InvalidFormatException e) {
      e.printStackTrace();
    }
catch (    OpenXML4JException e) {
      e.printStackTrace();
    }
    if (clone != null) {
      List<String> sheetlist=new ArrayList<String>();
      if (isXlsx && (EVENT_MODE).equals(generationMode)) {
        try {
          XSSFReader xssfReader=new XSSFReader(clone);
          XSSFReader.SheetIterator sheets=(XSSFReader.SheetIterator)xssfReader.getSheetsData();
          while (sheets.hasNext()) {
            sheets.next();
            String sheetName=sheets.getSheetName();
            sheetlist.add(sheetName);
          }
        }
 catch (        OpenXML4JException e) {
          CommonExceptionHandler.process(e);
        }
      }
 else {
        xwb=new XSSFWorkbook(clone);
        for (        XSSFSheet sheet : xwb) {
          sheetlist.add(sheet.getSheetName());
        }
      }
      sheetNamesForXlsx=new String[sheetlist.size()];
      for (int i=0; i < sheetlist.size(); i++) {
        sheetNamesForXlsx[i]=sheetlist.get(i);
      }
      sheetlist.clear();
    }
  }
}