JAVA POI关闭Workbook

     File f = new File("/path/to/excel/file");
     Workbook wb = null;

     NPOIFSFileSystem npoifs = null;
     OPCPackage pkg = null;
     try {
       npoifs = new NPOIFSFileSystem(f);
       wb = WorkbookFactory.create(npoifs);
     } catch(OfficeXmlFileException ofe) {
       pkg = OPCPackage.open(f);
       wb = WorkbookFactory.create(pkg);
     }


     if (npoifs != null) { npoifs.close(); }
     if (pkg != null) { pkg.close(); }