diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/apache-httpclient/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/apache-httpclient/ApiClient.mustache
index 6a26f2d8d8b4..0661db1e0ce8 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/apache-httpclient/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/apache-httpclient/ApiClient.mustache
@@ -622,7 +622,7 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
    * @param value The value of the parameter.
    * @return A list of {@code Pair} objects.
    */
-  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection value) {
+  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection<?> value) {
     List<Pair> params = new ArrayList<Pair>();
 
     // preconditions
diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache
index a641525af10a..730e975f7390 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/native/ApiClient.mustache
@@ -183,7 +183,7 @@ public class ApiClient {
     asyncResponseInterceptor = null;
   }
 
-  protected ObjectMapper createDefaultObjectMapper() {
+  public static ObjectMapper createDefaultObjectMapper() {
     ObjectMapper mapper = new ObjectMapper();
     mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
@@ -199,11 +199,11 @@ public class ApiClient {
     return mapper;
   }
 
-  protected String getDefaultBaseUri() {
+  private String getDefaultBaseUri() {
     return "{{{basePath}}}";
   }
 
-  protected HttpClient.Builder createDefaultHttpClientBuilder() {
+  public static HttpClient.Builder createDefaultHttpClientBuilder() {
     return HttpClient.newBuilder();
   }
 
diff --git a/samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java
index e6411ce783c9..ba3614d09d88 100644
--- a/samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/echo_api/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java
@@ -540,7 +540,7 @@ public List<Pair> parameterToPair(String name, Object value) {
    * @param value The value of the parameter.
    * @return A list of {@code Pair} objects.
    */
-  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection value) {
+  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection<?> value) {
     List<Pair> params = new ArrayList<Pair>();
 
     // preconditions
diff --git a/samples/client/echo_api/java/native/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/echo_api/java/native/src/main/java/org/openapitools/client/ApiClient.java
index e901d7f6f65b..e9ac66808052 100644
--- a/samples/client/echo_api/java/native/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/echo_api/java/native/src/main/java/org/openapitools/client/ApiClient.java
@@ -192,7 +192,7 @@ public ApiClient(HttpClient.Builder builder, ObjectMapper mapper, String baseUri
     asyncResponseInterceptor = null;
   }
 
-  protected ObjectMapper createDefaultObjectMapper() {
+  public static ObjectMapper createDefaultObjectMapper() {
     ObjectMapper mapper = new ObjectMapper();
     mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
@@ -206,11 +206,11 @@ protected ObjectMapper createDefaultObjectMapper() {
     return mapper;
   }
 
-  protected String getDefaultBaseUri() {
+  private String getDefaultBaseUri() {
     return "http://localhost:3000";
   }
 
-  protected HttpClient.Builder createDefaultHttpClientBuilder() {
+  public static HttpClient.Builder createDefaultHttpClientBuilder() {
     return HttpClient.newBuilder();
   }
 
diff --git a/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java
index 496412d49f36..ea63881b3508 100644
--- a/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/ApiClient.java
@@ -633,7 +633,7 @@ public List<Pair> parameterToPair(String name, Object value) {
    * @param value The value of the parameter.
    * @return A list of {@code Pair} objects.
    */
-  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection value) {
+  public List<Pair> parameterToPairs(String collectionFormat, String name, Collection<?> value) {
     List<Pair> params = new ArrayList<Pair>();
 
     // preconditions
diff --git a/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/ApiClient.java
index db109f5ce505..3b404f212839 100644
--- a/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/ApiClient.java
@@ -192,7 +192,7 @@ public ApiClient(HttpClient.Builder builder, ObjectMapper mapper, String baseUri
     asyncResponseInterceptor = null;
   }
 
-  protected ObjectMapper createDefaultObjectMapper() {
+  public static ObjectMapper createDefaultObjectMapper() {
     ObjectMapper mapper = new ObjectMapper();
     mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
@@ -206,11 +206,11 @@ protected ObjectMapper createDefaultObjectMapper() {
     return mapper;
   }
 
-  protected String getDefaultBaseUri() {
+  private String getDefaultBaseUri() {
     return "http://petstore.swagger.io:80/v2";
   }
 
-  protected HttpClient.Builder createDefaultHttpClientBuilder() {
+  public static HttpClient.Builder createDefaultHttpClientBuilder() {
     return HttpClient.newBuilder();
   }
 
diff --git a/samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/ApiClient.java
index e9ab4dc54511..e5c5cb2f425c 100644
--- a/samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/native-jakarta/src/main/java/org/openapitools/client/ApiClient.java
@@ -192,7 +192,7 @@ public ApiClient(HttpClient.Builder builder, ObjectMapper mapper, String baseUri
     asyncResponseInterceptor = null;
   }
 
-  protected ObjectMapper createDefaultObjectMapper() {
+  public static ObjectMapper createDefaultObjectMapper() {
     ObjectMapper mapper = new ObjectMapper();
     mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
@@ -206,11 +206,11 @@ protected ObjectMapper createDefaultObjectMapper() {
     return mapper;
   }
 
-  protected String getDefaultBaseUri() {
+  private String getDefaultBaseUri() {
     return "http://petstore.swagger.io/v2";
   }
 
-  protected HttpClient.Builder createDefaultHttpClientBuilder() {
+  public static HttpClient.Builder createDefaultHttpClientBuilder() {
     return HttpClient.newBuilder();
   }
 
diff --git a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/ApiClient.java
index db109f5ce505..3b404f212839 100644
--- a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/ApiClient.java
@@ -192,7 +192,7 @@ public ApiClient(HttpClient.Builder builder, ObjectMapper mapper, String baseUri
     asyncResponseInterceptor = null;
   }
 
-  protected ObjectMapper createDefaultObjectMapper() {
+  public static ObjectMapper createDefaultObjectMapper() {
     ObjectMapper mapper = new ObjectMapper();
     mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
@@ -206,11 +206,11 @@ protected ObjectMapper createDefaultObjectMapper() {
     return mapper;
   }
 
-  protected String getDefaultBaseUri() {
+  private String getDefaultBaseUri() {
     return "http://petstore.swagger.io:80/v2";
   }
 
-  protected HttpClient.Builder createDefaultHttpClientBuilder() {
+  public static HttpClient.Builder createDefaultHttpClientBuilder() {
     return HttpClient.newBuilder();
   }