diff --git a/modules/openapi-generator/src/main/resources/Java/RFC3339DateFormat.mustache b/modules/openapi-generator/src/main/resources/Java/RFC3339DateFormat.mustache
index 46c7bb46dc..311616a4ef 100644
--- a/modules/openapi-generator/src/main/resources/Java/RFC3339DateFormat.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/RFC3339DateFormat.mustache
@@ -7,6 +7,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -20,6 +21,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/apache-httpclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/feign-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/jersey2-java8-localdatetime/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/jersey2-java8-localdatetime/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/jersey2-java8-localdatetime/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/jersey2-java8-localdatetime/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/native-async/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/vertx-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/vertx-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/vertx-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/vertx-no-nullable/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/webclient-nulable-arrays/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/webclient-nulable-arrays/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index a713954ea4..5d3e6fbb11 100644
--- a/samples/client/petstore/java/webclient-nulable-arrays/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/webclient-nulable-arrays/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/openapi3/client/extensions/x-auth-id-alias/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/openapi3/client/extensions/x-auth-id-alias/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 455b7a6101..192e1d004d 100644
--- a/samples/openapi3/client/extensions/x-auth-id-alias/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/openapi3/client/extensions/x-auth-id-alias/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/openapi3/client/petstore/java/jersey2-java8-special-characters/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/openapi3/client/petstore/java/jersey2-java8-special-characters/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 01137208e9..1bbccf2340 100644
--- a/samples/openapi3/client/petstore/java/jersey2-java8-special-characters/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/openapi3/client/petstore/java/jersey2-java8-special-characters/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override
diff --git a/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java b/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
index 80397abe96..f94cba613b 100644
--- a/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
+++ b/samples/openapi3/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/RFC3339DateFormat.java
@@ -18,6 +18,7 @@ import java.text.DateFormat;
 import java.text.FieldPosition;
 import java.text.ParsePosition;
 import java.util.Date;
+import java.text.DecimalFormat;
 import java.util.GregorianCalendar;
 import java.util.TimeZone;
 
@@ -31,6 +32,7 @@ public class RFC3339DateFormat extends DateFormat {
 
   public RFC3339DateFormat() {
     this.calendar = new GregorianCalendar();
+    this.numberFormat = new DecimalFormat();
   }
 
   @Override