Cleanup imports and comments in V3 stubs.

PiperOrigin-RevId: 644154501

java/core/src/main/java/com/google/protobuf/GeneratedMessageV3.java

@@ -1,5 +1,5 @@
 // Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
+// Copyright 2024 Google LLC.  All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at
@@ -9,13 +9,6 @@ package com.google.protobuf;
 
 import java.util.List;
 
-import com.google.protobuf.Descriptors.Descriptor;
-import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Extension.ExtensionType;
-import com.google.protobuf.GeneratedMessage.ExtendableMessageOrBuilder;
-import com.google.protobuf.GeneratedMessage.ExtensionDescriptorRetriever;
-import com.google.protobuf.GeneratedMessage.FieldAccessorTable;
-
 /**
  * Stub for GeneratedMessageV3 wrapping GeneratedMessage for compatibility with older gencode.
  *
@@ -48,7 +41,7 @@ public abstract class GeneratedMessageV3 extends GeneratedMessage {
           MessageT extends ExtendableMessage<MessageT>,
           BuilderT extends ExtendableBuilder<MessageT, BuilderT>>
       extends GeneratedMessage.ExtendableBuilder<MessageT, BuilderT>
-      implements ExtendableMessageOrBuilder<MessageT> {
+      implements GeneratedMessage.ExtendableMessageOrBuilder<MessageT> {
     protected ExtendableBuilder() {
       super();
     }
@@ -57,13 +50,15 @@ public abstract class GeneratedMessageV3 extends GeneratedMessage {
       super(parent);
     }
 
-    // Support old gencode override method removed in cl/597677225
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
     public <T> BuilderT setExtension(
         final GeneratedMessage.GeneratedExtension<MessageT, T> extension, final T value) {
       return setExtension((ExtensionLite<MessageT, T>) extension, value);
     }
 
-    // Support old gencode override method removed in cl/597677225
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
     public <T> BuilderT setExtension(
         final GeneratedMessage.GeneratedExtension<MessageT, List<T>> extension,
         final int index,
@@ -71,13 +66,15 @@ public abstract class GeneratedMessageV3 extends GeneratedMessage {
       return setExtension((ExtensionLite<MessageT, List<T>>) extension, index, value);
     }
 
-    // Support old gencode override method removed in cl/597677225
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
     public <T> BuilderT addExtension(
         final GeneratedMessage.GeneratedExtension<MessageT, List<T>> extension, final T value) {
       return addExtension((ExtensionLite<MessageT, List<T>>) extension, value);
     }
 
-    // Support old gencode override method removed in cl/597677225
+    // Support old gencode override method removed in
+    // https://github.com/protocolbuffers/protobuf/commit/7bff169d32710b143951ec6ce2c4ea9a56e2ad24
     public <T> BuilderT clearExtension(
         final GeneratedMessage.GeneratedExtension<MessageT, T> extension) {
       return clearExtension((ExtensionLite<MessageT, T>) extension);

java/core/src/main/java/com/google/protobuf/RepeatedFieldBuilderV3.java

@@ -1,5 +1,5 @@
 // Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
+// Copyright 2024 Google LLC.  All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at

java/core/src/main/java/com/google/protobuf/SingleFieldBuilderV3.java

@@ -1,5 +1,5 @@
 // Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc.  All rights reserved.
+// Copyright 2024 Google LLC.  All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at
@@ -7,8 +7,6 @@
 
 package com.google.protobuf;
 
-import static com.google.protobuf.Internal.checkNotNull;
-
 /**
  * Stub for SingleFieldBuilderV3 wrapping SingleFieldBuilder for compatibility with older gencode.
  *