how to validate null in substring in thymeleaf code example

Example 1: thymeleaf is string empty

<p th:text="${#strings.isEmpty(string)}"></p>
<p th:text="${#strings.isEmpty(nullString)}"></p>
<p th:text="${#strings.defaultString(emptyString,'Empty String')}"></p>

Example 2: thymeleaf strings is not empty

<div th:if= "${searchResults.results != null}">