diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/restclient/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/restclient/ApiClient.mustache
index 67bf59b0d1bb..23c4a74cd0f3 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/restclient/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/restclient/ApiClient.mustache
@@ -107,12 +107,12 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -648,7 +648,7 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/modules/openapi-generator/src/main/resources/Java/libraries/webclient/ApiClient.mustache b/modules/openapi-generator/src/main/resources/Java/libraries/webclient/ApiClient.mustache
index 6209b2334de2..e172ac048ca0 100644
--- a/modules/openapi-generator/src/main/resources/Java/libraries/webclient/ApiClient.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/libraries/webclient/ApiClient.mustache
@@ -110,12 +110,12 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -549,7 +549,7 @@ public class ApiClient{{#jsr310}} extends JavaTimeFormatter{{/jsr310}} {
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/echo_api/java/restclient/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/echo_api/java/restclient/src/main/java/org/openapitools/client/ApiClient.java
index 05bbc02f8f85..8cc3ac215066 100644
--- a/samples/client/echo_api/java/restclient/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/echo_api/java/restclient/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -495,7 +495,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/others/java/restclient-enum-in-multipart/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/restclient-enum-in-multipart/src/main/java/org/openapitools/client/ApiClient.java
index df5351da7a94..8533a16386fb 100644
--- a/samples/client/others/java/restclient-enum-in-multipart/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/restclient-enum-in-multipart/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -494,7 +494,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/others/java/restclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/restclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java
index 6defd1f39f76..dc5f98f6058f 100644
--- a/samples/client/others/java/restclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/restclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -493,7 +493,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/others/java/restclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/restclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java
index c6b2bd029cf3..6e4fc0d1af45 100644
--- a/samples/client/others/java/restclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/restclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -493,7 +493,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/others/java/webclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/webclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java
index 94e98d60fb3c..72fcfbdab230 100644
--- a/samples/client/others/java/webclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/webclient-sealedInterface/src/main/java/org/openapitools/client/ApiClient.java
@@ -86,12 +86,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -468,7 +468,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ApiClient.java
index 94e98d60fb3c..72fcfbdab230 100644
--- a/samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/webclient-sealedInterface_3_1/src/main/java/org/openapitools/client/ApiClient.java
@@ -86,12 +86,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -468,7 +468,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/others/java/webclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/others/java/webclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java
index d9d027fa55b6..cda7ccc6b967 100644
--- a/samples/client/others/java/webclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/others/java/webclient-useAbstractionForFiles/src/main/java/org/openapitools/client/ApiClient.java
@@ -86,12 +86,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -468,7 +468,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java
index 55de060e485a..628f6527c2fd 100644
--- a/samples/client/petstore/java/restclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -493,7 +493,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-springBoot4-jackson2/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-springBoot4-jackson2/src/main/java/org/openapitools/client/ApiClient.java
index 2b11f9a0dff0..825b56546fd8 100644
--- a/samples/client/petstore/java/restclient-springBoot4-jackson2/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-springBoot4-jackson2/src/main/java/org/openapitools/client/ApiClient.java
@@ -69,12 +69,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -519,7 +519,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify-openapiNullable/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify-openapiNullable/src/main/java/org/openapitools/client/ApiClient.java
index adabd72b33be..5b3f0ecc6a5d 100644
--- a/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify-openapiNullable/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify-openapiNullable/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -491,7 +491,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java
index b7ba98b02426..6b2cf59a04f8 100644
--- a/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java
@@ -67,12 +67,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -489,7 +489,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java
index 488326e79a14..73fbfede75e5 100644
--- a/samples/client/petstore/java/restclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java
@@ -68,12 +68,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -515,7 +515,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java
index 92bcdca82488..9f7e67e4af9e 100644
--- a/samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java
@@ -69,12 +69,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -566,7 +566,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/ApiClient.java
index 92bcdca82488..9f7e67e4af9e 100644
--- a/samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-useSingleRequestParameter-static/src/main/java/org/openapitools/client/ApiClient.java
@@ -69,12 +69,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -566,7 +566,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java
index 92bcdca82488..9f7e67e4af9e 100644
--- a/samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java
@@ -69,12 +69,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -566,7 +566,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/restclient/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/restclient/src/main/java/org/openapitools/client/ApiClient.java
index 92bcdca82488..9f7e67e4af9e 100644
--- a/samples/client/petstore/java/restclient/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/restclient/src/main/java/org/openapitools/client/ApiClient.java
@@ -69,12 +69,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -566,7 +566,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient-jakarta/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient-jakarta/src/main/java/org/openapitools/client/ApiClient.java
index e6da0d43615b..e050a9523651 100644
--- a/samples/client/petstore/java/webclient-jakarta/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient-jakarta/src/main/java/org/openapitools/client/ApiClient.java
@@ -87,12 +87,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -488,7 +488,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java
index a9c15fc5a9af..b9e80a960e4b 100644
--- a/samples/client/petstore/java/webclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient-nullable-arrays/src/main/java/org/openapitools/client/ApiClient.java
@@ -86,12 +86,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -468,7 +468,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java
index 1c8596bcea7b..5362e6398083 100644
--- a/samples/client/petstore/java/webclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient-springBoot4-jackson3-jspecify/src/main/java/org/openapitools/client/ApiClient.java
@@ -84,12 +84,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -463,7 +463,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java
index cb7005c02930..9ee93507cdc1 100644
--- a/samples/client/petstore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient-springBoot4-jackson3/src/main/java/org/openapitools/client/ApiClient.java
@@ -85,12 +85,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -479,7 +479,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java
index f1ddbf78b3a0..74affaa2c3e7 100644
--- a/samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient-swagger2/src/main/java/org/openapitools/client/ApiClient.java
@@ -87,12 +87,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -488,7 +488,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java
index f1ddbf78b3a0..74affaa2c3e7 100644
--- a/samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient-useSingleRequestParameter/src/main/java/org/openapitools/client/ApiClient.java
@@ -87,12 +87,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -488,7 +488,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**
diff --git a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ApiClient.java b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ApiClient.java
index f1ddbf78b3a0..74affaa2c3e7 100644
--- a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ApiClient.java
+++ b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/ApiClient.java
@@ -87,12 +87,12 @@ public class ApiClient extends JavaTimeFormatter {
     public enum CollectionFormat {
         CSV(","), TSV("\t"), SSV(" "), PIPES("|"), MULTI(null);
 
-        protected final String separator;
+        private final String separator;
         CollectionFormat(String separator) {
             this.separator = separator;
         }
 
-        protected String collectionToString(Collection<?> collection) {
+        public String collectionToString(Collection<?> collection) {
             return StringUtils.collectionToDelimitedString(collection, separator);
         }
     }
@@ -488,7 +488,7 @@ public MultiValueMap<String, String> parameterToMultiValueMapJson(CollectionForm
                 throw exceptionProvider.jacksonException(e);
             }
         }
-        return parameterToMultiValueMap(collectionFormat, name, "[" + StringUtils.collectionToDelimitedString(values, collectionFormat.separator) + "]");
+        return parameterToMultiValueMap(collectionFormat, name, "[" + collectionFormat.collectionToString(values) + "]");
     }
 
     /**