class ImporterSpreadsheetExcelBuilder implements FileImporterBuilder {

    public static final String IDENTIFER = "spreadsheet_excel";
    public static final String[] EXTENSIONS = new String[] {".xls", ".xlsx"};

    @Override
    public FileImporter buildImporter() {
        return new ImporterSpreadsheetExcel();
    }

    @Override
    public String getName() {
        return IDENTIFER;
    }

    @Override
    public FileType[] getFileTypes() {
        return new FileType[] {
            new FileType(EXTENSIONS, NbBundle.getMessage(getClass(), "fileType_Spreadsheet_Name"))
        };
    }

    @Override
    public boolean isMatchingImporter(FileObject fileObject) {<FILL_FUNCTION_BODY>}
}

        for (String ext : EXTENSIONS) {
            if (fileObject.getExt().equalsIgnoreCase(ext.substring(1))) {
                return true;
            }
        }

        return false;
    
<no_super_class>