如何用新字符串更新空字符串？

Question

<tbody>
                         <tr th:each="bill : ${bills}">
                                <td><a th:text="${bill.invoiceNum}" th:href="@{'/show/' + ${bill.id}}"></a></td>
                                <td th:text="${bill.invoiceDate}"></td>
                                <td th:text="${bill.receiverName}"></td>
                                <td th:text="${bill.receiverAddress}"></td>
                                <td th:text="${bill.receiverState}"></td>
                                <td th:text="${bill.receiverGstNum}"></td>
                                <td th:text="${bill.propertyAddress}"></td>
                                <td th:text="${#numbers.formatDecimal(bill.brokerageRate,3,2)}"></td>
                                <td th:text="${bill.brokerageAmount}"></td>
                                <td th:text="${bill.cgstPct}"></td>
                                <td th:text="${bill.cgstAmount}"></td>
                                <td th:text="${bill.sgstPct}"></td>
                                <td th:text="${bill.sgstAmount}"></td>
                                <td th:text="${bill.igstPct}"></td>
                                <td th:text="${bill.igstAmount}"></td>
                                <td th:text="${bill.totalGstAmount}"></td>
                                <td th:text="${bill.brokerageDueAfterTax}"></td>
                            </tr>
                        </tbody>

如何使用新字符串更新空字符串