diff --git a/src/main/java/io/numaproj/numaflow/accumulator/OutputStreamObserverImpl.java b/src/main/java/io/numaproj/numaflow/accumulator/OutputStreamObserverImpl.java
index 24811de6..7c730507 100644
--- a/src/main/java/io/numaproj/numaflow/accumulator/OutputStreamObserverImpl.java
+++ b/src/main/java/io/numaproj/numaflow/accumulator/OutputStreamObserverImpl.java
@@ -10,7 +10,6 @@
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.List;
 
 class OutputStreamObserverImpl implements OutputStreamObserver {
     private final ActorRef outputActor;
@@ -58,7 +57,7 @@ private AccumulatorOuterClass.AccumulatorResponse buildResponse(Message message)
                         .setId(message.getId())
                         .build())
                 .addAllTags(
-                        message.getTags() == null ? new ArrayList<>() : List.of(message.getTags()))
+                        message.getTags() == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                 .build();
     }
 
diff --git a/src/main/java/io/numaproj/numaflow/batchmapper/Service.java b/src/main/java/io/numaproj/numaflow/batchmapper/Service.java
index fbd103be..4be3b812 100644
--- a/src/main/java/io/numaproj/numaflow/batchmapper/Service.java
+++ b/src/main/java/io/numaproj/numaflow/batchmapper/Service.java
@@ -16,6 +16,7 @@
 
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutorService;
@@ -150,9 +151,9 @@ private void buildAndStreamResponse(
                                             == null ? ByteString.EMPTY : ByteString.copyFrom(
                                             res.getValue()))
                                     .addAllKeys(res.getKeys()
-                                            == null ? new ArrayList<>() : List.of(res.getKeys()))
+                                            == null ? new ArrayList<>() : Arrays.asList(res.getKeys()))
                                     .addAllTags(res.getTags()
-                                            == null ? new ArrayList<>() : List.of(res.getTags()))
+                                            == null ? new ArrayList<>() : Arrays.asList(res.getTags()))
                                     .build()
                     );
                 });
diff --git a/src/main/java/io/numaproj/numaflow/mapper/MapperActor.java b/src/main/java/io/numaproj/numaflow/mapper/MapperActor.java
index 316c35a6..a6a56078 100644
--- a/src/main/java/io/numaproj/numaflow/mapper/MapperActor.java
+++ b/src/main/java/io/numaproj/numaflow/mapper/MapperActor.java
@@ -9,7 +9,7 @@
 
 import java.time.Instant;
 import java.util.ArrayList;
-import java.util.List;
+import java.util.Arrays;
 
 /**
  * Mapper actor that processes the map request. It invokes the mapper to process the request and
@@ -86,9 +86,9 @@ private MapOuterClass.MapResponse buildResponse(MessageList messageList, String
                     .setValue(message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
                             message.getValue()))
                     .addAllKeys(message.getKeys()
-                            == null ? new ArrayList<>() : List.of(message.getKeys()))
+                            == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                     .addAllTags(message.getTags()
-                            == null ? new ArrayList<>() : List.of(message.getTags()))
+                            == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                     .build());
         });
         return responseBuilder.setId(ID).build();
diff --git a/src/main/java/io/numaproj/numaflow/mapper/MapperTestKit.java b/src/main/java/io/numaproj/numaflow/mapper/MapperTestKit.java
index e2612dc3..9567568f 100644
--- a/src/main/java/io/numaproj/numaflow/mapper/MapperTestKit.java
+++ b/src/main/java/io/numaproj/numaflow/mapper/MapperTestKit.java
@@ -13,6 +13,7 @@
 
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -160,7 +161,7 @@ private MapOuterClass.MapRequest createRequest(
                 String requestId) {
             return MapOuterClass.MapRequest.newBuilder().setRequest(
                     MapOuterClass.MapRequest.Request.newBuilder()
-                            .addAllKeys(keys == null ? new ArrayList<>() : List.of(keys))
+                            .addAllKeys(keys == null ? new ArrayList<>() : Arrays.asList(keys))
                             .setValue(data.getValue()
                                     == null ? ByteString.EMPTY : ByteString.copyFrom(data.getValue()))
                             .setEventTime(
diff --git a/src/main/java/io/numaproj/numaflow/mapstreamer/OutputObserverImpl.java b/src/main/java/io/numaproj/numaflow/mapstreamer/OutputObserverImpl.java
index af641419..0a008b48 100644
--- a/src/main/java/io/numaproj/numaflow/mapstreamer/OutputObserverImpl.java
+++ b/src/main/java/io/numaproj/numaflow/mapstreamer/OutputObserverImpl.java
@@ -6,7 +6,7 @@
 import lombok.AllArgsConstructor;
 
 import java.util.ArrayList;
-import java.util.List;
+import java.util.Arrays;
 
 /**
  * Implementation of the OutputObserver interface.
@@ -36,9 +36,9 @@ public void send(Message message) {
                                 message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
                                         message.getValue()))
                         .addAllKeys(message.getKeys()
-                                == null ? new ArrayList<>() : List.of(message.getKeys()))
+                                == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                         .addAllTags(message.getTags()
-                                == null ? new ArrayList<>() : List.of(message.getTags()))
+                                == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                         .build()).build();
         supervisorActor.tell(response, ActorRef.noSender());
     }
diff --git a/src/main/java/io/numaproj/numaflow/reducer/ReduceActor.java b/src/main/java/io/numaproj/numaflow/reducer/ReduceActor.java
index 327354a0..d5ca690f 100644
--- a/src/main/java/io/numaproj/numaflow/reducer/ReduceActor.java
+++ b/src/main/java/io/numaproj/numaflow/reducer/ReduceActor.java
@@ -11,7 +11,6 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.List;
 
 /**
  * Reduce actor invokes the reducer and returns the result.
@@ -70,7 +69,7 @@ private ActorResponse buildActorResponse(Message message) {
                 .addAllKeys(message.getKeys()
                         == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                 .addAllTags(
-                        message.getTags() == null ? new ArrayList<>() : List.of(message.getTags()))
+                        message.getTags() == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                 .build());
         return new ActorResponse(responseBuilder.build());
     }
@@ -89,7 +88,7 @@ private ActorResponse buildEOFActorResponse() {
         // set a dummy result with the keys.
         responseBuilder.setResult(ReduceOuterClass.ReduceResponse.Result
                 .newBuilder()
-                .addAllKeys(List.of(this.keys))
+                .addAllKeys(Arrays.asList(this.keys))
                 .build());
         return new ActorResponse(responseBuilder.build());
     }
diff --git a/src/main/java/io/numaproj/numaflow/reducestreamer/OutputStreamObserverImpl.java b/src/main/java/io/numaproj/numaflow/reducestreamer/OutputStreamObserverImpl.java
index 688fecaf..c28eca49 100644
--- a/src/main/java/io/numaproj/numaflow/reducestreamer/OutputStreamObserverImpl.java
+++ b/src/main/java/io/numaproj/numaflow/reducestreamer/OutputStreamObserverImpl.java
@@ -11,7 +11,6 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.List;
 
 @AllArgsConstructor
 class OutputStreamObserverImpl implements OutputStreamObserver {
@@ -42,7 +41,7 @@ private ActorResponse buildResponse(Message message) {
                 .addAllKeys(message.getKeys()
                         == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                 .addAllTags(
-                        message.getTags() == null ? new ArrayList<>() : List.of(message.getTags()))
+                        message.getTags() == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                 .build());
         return new ActorResponse(responseBuilder.build());
     }
diff --git a/src/main/java/io/numaproj/numaflow/reducestreamer/ReduceStreamerActor.java b/src/main/java/io/numaproj/numaflow/reducestreamer/ReduceStreamerActor.java
index e1704433..4e5c15f3 100644
--- a/src/main/java/io/numaproj/numaflow/reducestreamer/ReduceStreamerActor.java
+++ b/src/main/java/io/numaproj/numaflow/reducestreamer/ReduceStreamerActor.java
@@ -11,7 +11,7 @@
 import io.numaproj.numaflow.reducestreamer.model.ReduceStreamer;
 import lombok.AllArgsConstructor;
 
-import java.util.List;
+import java.util.Arrays;
 
 /**
  * Reduce streamer actor invokes user defined functions to handle reduce requests.
@@ -71,7 +71,7 @@ private ActorResponse buildEOFResponse() {
         // set a dummy result with the keys.
         responseBuilder.setResult(ReduceOuterClass.ReduceResponse.Result
                 .newBuilder()
-                .addAllKeys(List.of(this.keys))
+                .addAllKeys(Arrays.asList(this.keys))
                 .build());
         return new ActorResponse(responseBuilder.build());
     }
diff --git a/src/main/java/io/numaproj/numaflow/sessionreducer/OutputStreamObserverImpl.java b/src/main/java/io/numaproj/numaflow/sessionreducer/OutputStreamObserverImpl.java
index 95f2307a..421ea073 100644
--- a/src/main/java/io/numaproj/numaflow/sessionreducer/OutputStreamObserverImpl.java
+++ b/src/main/java/io/numaproj/numaflow/sessionreducer/OutputStreamObserverImpl.java
@@ -10,7 +10,6 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.List;
 
 /**
  * OutputStreamObserverImpl transforms a message to an ActorResponse.
@@ -42,7 +41,7 @@ private ActorResponse buildResponse(Message message, Sessionreduce.KeyedWindow k
                 .addAllKeys(message.getKeys()
                         == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                 .addAllTags(
-                        message.getTags() == null ? new ArrayList<>() : List.of(message.getTags()))
+                        message.getTags() == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                 .build());
         return ActorResponse.builder()
                 .response(responseBuilder.build())
diff --git a/src/main/java/io/numaproj/numaflow/sinker/SinkerTestKit.java b/src/main/java/io/numaproj/numaflow/sinker/SinkerTestKit.java
index f6708d4a..efa8a9d4 100644
--- a/src/main/java/io/numaproj/numaflow/sinker/SinkerTestKit.java
+++ b/src/main/java/io/numaproj/numaflow/sinker/SinkerTestKit.java
@@ -16,6 +16,7 @@
 import java.io.IOException;
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -157,7 +158,7 @@ public void onCompleted() {
                         .newBuilder()
                         .addAllKeys(
                                 datum.getKeys()
-                                        == null ? new ArrayList<>() : List.of(datum.getKeys()))
+                                        == null ? new ArrayList<>() : Arrays.asList(datum.getKeys()))
                         .setValue(datum.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
                                 datum.getValue()))
                         .setId(datum.getId())
diff --git a/src/main/java/io/numaproj/numaflow/sourcer/OutputObserverImpl.java b/src/main/java/io/numaproj/numaflow/sourcer/OutputObserverImpl.java
index dbc004a0..14a23543 100644
--- a/src/main/java/io/numaproj/numaflow/sourcer/OutputObserverImpl.java
+++ b/src/main/java/io/numaproj/numaflow/sourcer/OutputObserverImpl.java
@@ -7,8 +7,8 @@
 import lombok.AllArgsConstructor;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
-import java.util.List;
 
 /**
  * OutputObserverImpl is the implementation of the OutputObserver interface.
@@ -29,7 +29,7 @@ private SourceOuterClass.ReadResponse buildResponse(Message message) {
                 .newBuilder()
                 .setResult(SourceOuterClass.ReadResponse.Result.newBuilder()
                         .addAllKeys(message.getKeys()
-                                == null ? new ArrayList<>() : List.of(message.getKeys()))
+                                == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                         .setPayload(
                                 message.getValue() == null ? ByteString.EMPTY : ByteString.copyFrom(
                                         message.getValue()))
diff --git a/src/main/java/io/numaproj/numaflow/sourcetransformer/SourceTransformerTestKit.java b/src/main/java/io/numaproj/numaflow/sourcetransformer/SourceTransformerTestKit.java
index 9ab1cc44..bc600a94 100644
--- a/src/main/java/io/numaproj/numaflow/sourcetransformer/SourceTransformerTestKit.java
+++ b/src/main/java/io/numaproj/numaflow/sourcetransformer/SourceTransformerTestKit.java
@@ -13,6 +13,7 @@
 
 import java.time.Instant;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -158,7 +159,7 @@ private Sourcetransformer.SourceTransformRequest createRequest(
                 String requestId) {
             return Sourcetransformer.SourceTransformRequest.newBuilder().setRequest(
                     Sourcetransformer.SourceTransformRequest.Request.newBuilder()
-                            .addAllKeys(keys == null ? new ArrayList<>() : List.of(keys))
+                            .addAllKeys(keys == null ? new ArrayList<>() : Arrays.asList(keys))
                             .setValue(data.getValue()
                                     == null ? ByteString.EMPTY : ByteString.copyFrom(data.getValue()))
                             .setEventTime(
diff --git a/src/main/java/io/numaproj/numaflow/sourcetransformer/TransformerActor.java b/src/main/java/io/numaproj/numaflow/sourcetransformer/TransformerActor.java
index b2e744cd..08f67a06 100644
--- a/src/main/java/io/numaproj/numaflow/sourcetransformer/TransformerActor.java
+++ b/src/main/java/io/numaproj/numaflow/sourcetransformer/TransformerActor.java
@@ -9,7 +9,7 @@
 
 import java.time.Instant;
 import java.util.ArrayList;
-import java.util.List;
+import java.util.Arrays;
 
 /**
  * TransformerActor is an actor that processes the SourceTransformRequest.
@@ -114,9 +114,9 @@ private Sourcetransformer.SourceTransformResponse buildResponse(
                                     .getEpochSecond())
                             .setNanos(message.getEventTime().getNano()))
                     .addAllKeys(message.getKeys()
-                            == null ? new ArrayList<>() : List.of(message.getKeys()))
+                            == null ? new ArrayList<>() : Arrays.asList(message.getKeys()))
                     .addAllTags(message.getTags()
-                            == null ? new ArrayList<>() : List.of(message.getTags()))
+                            == null ? new ArrayList<>() : Arrays.asList(message.getTags()))
                     .build());
         });
         return responseBuilder.setId(ID).build();