diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/restclient/api.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/restclient/api.mustache
index 66dd26b4fd60..cb1e3e429c4d 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/restclient/api.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/restclient/api.mustache
@@ -180,7 +180,7 @@ public class {{classname}} {
     {{#isDeprecated}}
     @Deprecated
     {{/isDeprecated}}
-    public {{#returnType}}{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{returnType}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{returnType}}}{{/isResponseFile}} {{/returnType}}{{^returnType}}void {{/returnType}}{{operationId}}({{#allParams}}{{#isFile}}{{#useAbstractionForFiles}}{{#collectionFormat}}java.util.Collection<org.springframework.core.io.Resource>{{/collectionFormat}}{{^collectionFormat}}org.springframework.core.io.Resource{{/collectionFormat}}{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{>nullableArgument}}{{/useAbstractionForFiles}}{{/isFile}}{{^isFile}}{{>nullable_var_annotations}} {{{dataType}}}{{/isFile}} {{paramName}}{{^-last}}, {{/-last}}{{/allParams}}) throws RestClientResponseException {
+    public {{#returnType}}{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{returnType}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{returnType}}}{{/isResponseFile}} {{/returnType}}{{^returnType}}void {{/returnType}}{{operationId}}({{#allParams}}{{#isFile}}{{#useAbstractionForFiles}}{{#collectionFormat}}java.util.Collection<org.springframework.core.io.Resource>{{/collectionFormat}}{{^collectionFormat}}org.springframework.core.io.Resource{{/collectionFormat}}{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{>nullableArgument}}{{/useAbstractionForFiles}}{{/isFile}}{{^isFile}}{{>nullableArgument}}{{/isFile}} {{paramName}}{{^-last}}, {{/-last}}{{/allParams}}) throws RestClientResponseException {
         {{#returnType}}ParameterizedTypeReference<{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{returnType}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{returnType}}}{{/isResponseFile}}> localVarReturnType = new ParameterizedTypeReference<>() {};{{/returnType}}{{^returnType}}ParameterizedTypeReference<Void> localVarReturnType = new ParameterizedTypeReference<>() {};{{/returnType}}
         {{#returnType}}return {{/returnType}}{{operationId}}RequestCreation({{#allParams}}{{paramName}}{{^-last}}, {{/-last}}{{/allParams}}).body(localVarReturnType);
     }
@@ -203,7 +203,7 @@ public class {{classname}} {
     {{#isDeprecated}}
     @Deprecated
     {{/isDeprecated}}
-    public {{#returnType}}ResponseEntity<{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{returnType}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{returnType}}}{{/isResponseFile}}>{{/returnType}}{{^returnType}}ResponseEntity<Void>{{/returnType}} {{operationId}}WithHttpInfo({{#allParams}}{{#isFile}}{{#useAbstractionForFiles}}{{#collectionFormat}}java.util.Collection<org.springframework.core.io.Resource>{{/collectionFormat}}{{^collectionFormat}}org.springframework.core.io.Resource{{/collectionFormat}}{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{>nullableArgument}}{{/useAbstractionForFiles}}{{/isFile}}{{^isFile}}{{>nullable_var_annotations}} {{{dataType}}}{{/isFile}} {{paramName}}{{^-last}}, {{/-last}}{{/allParams}}) throws RestClientResponseException {
+    public {{#returnType}}ResponseEntity<{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{returnType}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{returnType}}}{{/isResponseFile}}>{{/returnType}}{{^returnType}}ResponseEntity<Void>{{/returnType}} {{operationId}}WithHttpInfo({{#allParams}}{{#isFile}}{{#useAbstractionForFiles}}{{#collectionFormat}}java.util.Collection<org.springframework.core.io.Resource>{{/collectionFormat}}{{^collectionFormat}}org.springframework.core.io.Resource{{/collectionFormat}}{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{>nullableArgument}}{{/useAbstractionForFiles}}{{/isFile}}{{^isFile}}{{>nullableArgument}}{{/isFile}} {{paramName}}{{^-last}}, {{/-last}}{{/allParams}}) throws RestClientResponseException {
         {{#returnType}}ParameterizedTypeReference<{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{returnType}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{returnType}}}{{/isResponseFile}}> localVarReturnType = new ParameterizedTypeReference<>() {};{{/returnType}}{{^returnType}}ParameterizedTypeReference<Void> localVarReturnType = new ParameterizedTypeReference<>() {};{{/returnType}}
         return {{operationId}}RequestCreation({{#allParams}}{{paramName}}{{^-last}}, {{/-last}}{{/allParams}}).toEntity(localVarReturnType);
     }
diff --git a/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/api/DefaultApi.java b/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/api/DefaultApi.java
index 5c44d1841571..416d0a561343 100644
--- a/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/api/DefaultApi.java
+++ b/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/api/DefaultApi.java
@@ -88,7 +88,7 @@ private ResponseSpec fileIdGetRequestCreation(String id) throws RestClientRespon
      * @param id The id parameter
      * @throws RestClientResponseException if an error occurs while attempting to invoke the API
      */
-    public void fileIdGet( String id) throws RestClientResponseException {
+    public void fileIdGet(String id) throws RestClientResponseException {
         ParameterizedTypeReference<Void> localVarReturnType = new ParameterizedTypeReference<>() {};
         fileIdGetRequestCreation(id).body(localVarReturnType);
     }
@@ -100,7 +100,7 @@ public void fileIdGet( String id) throws RestClientResponseException {
      * @param id The id parameter
      * @throws RestClientResponseException if an error occurs while attempting to invoke the API
      */
-    public ResponseEntity<Void> fileIdGetWithHttpInfo( String id) throws RestClientResponseException {
+    public ResponseEntity<Void> fileIdGetWithHttpInfo(String id) throws RestClientResponseException {
         ParameterizedTypeReference<Void> localVarReturnType = new ParameterizedTypeReference<>() {};
         return fileIdGetRequestCreation(id).toEntity(localVarReturnType);
     }
@@ -166,7 +166,7 @@ private ResponseSpec fooDtParamGetRequestCreation(java.time.@Nullable Instant dt
      * @return Foo
      * @throws RestClientResponseException if an error occurs while attempting to invoke the API
      */
-    public Foo fooDtParamGet( java.time.Instant dtParam,  java.time.Instant dtQuery,  java.time.Instant dtCookie) throws RestClientResponseException {
+    public Foo fooDtParamGet(java.time.@Nullable Instant dtParam, java.time.@Nullable Instant dtQuery, java.time.@Nullable Instant dtCookie) throws RestClientResponseException {
         ParameterizedTypeReference<Foo> localVarReturnType = new ParameterizedTypeReference<>() {};
         return fooDtParamGetRequestCreation(dtParam, dtQuery, dtCookie).body(localVarReturnType);
     }
@@ -181,7 +181,7 @@ public Foo fooDtParamGet( java.time.Instant dtParam,  java.time.Instant dtQuery,
      * @return ResponseEntity&lt;Foo&gt;
      * @throws RestClientResponseException if an error occurs while attempting to invoke the API
      */
-    public ResponseEntity<Foo> fooDtParamGetWithHttpInfo( java.time.Instant dtParam,  java.time.Instant dtQuery,  java.time.Instant dtCookie) throws RestClientResponseException {
+    public ResponseEntity<Foo> fooDtParamGetWithHttpInfo(java.time.@Nullable Instant dtParam, java.time.@Nullable Instant dtQuery, java.time.@Nullable Instant dtCookie) throws RestClientResponseException {
         ParameterizedTypeReference<Foo> localVarReturnType = new ParameterizedTypeReference<>() {};
         return fooDtParamGetRequestCreation(dtParam, dtQuery, dtCookie).toEntity(localVarReturnType);
     }