KAFKA-16643 Add ModifierOrder checkstyle rule

checkstyle/checkstyle.xml

@@ -150,6 +150,9 @@
 
     <!-- Allows the use of the @SuppressWarnings annotation in the code -->
     <module name="SuppressWarningsHolder"/>
+
+    <module name="ModifierOrder"/>
+
   </module>
 
   <module name="SuppressionFilter">

clients/src/main/java/org/apache/kafka/clients/ClusterConnectionStates.java

@@ -37,10 +37,10 @@
  *
  */
 final class ClusterConnectionStates {
-    final static int RECONNECT_BACKOFF_EXP_BASE = 2;
-    final static double RECONNECT_BACKOFF_JITTER = 0.2;
-    final static int CONNECTION_SETUP_TIMEOUT_EXP_BASE = 2;
-    final static double CONNECTION_SETUP_TIMEOUT_JITTER = 0.2;
+    static final int RECONNECT_BACKOFF_EXP_BASE = 2;
+    static final double RECONNECT_BACKOFF_JITTER = 0.2;
+    static final int CONNECTION_SETUP_TIMEOUT_EXP_BASE = 2;
+    static final double CONNECTION_SETUP_TIMEOUT_JITTER = 0.2;
     private final Map<String, NodeConnectionState> nodeState;
     private final Logger log;
     private final HostResolver hostResolver;

clients/src/main/java/org/apache/kafka/clients/admin/CreateTopicsResult.java

@@ -32,7 +32,7 @@
  */
 @InterfaceStability.Evolving
 public class CreateTopicsResult {
-    final static int UNKNOWN = -1;
+    static final int UNKNOWN = -1;
 
     private final Map<String, KafkaFuture<TopicMetadataAndConfig>> futures;
 

clients/src/main/java/org/apache/kafka/clients/admin/DescribeReplicaLogDirsResult.java

@@ -66,7 +66,7 @@ public KafkaFuture<Map<TopicPartitionReplica, ReplicaLogDirInfo>> all() {
             });
     }
 
-    static public class ReplicaLogDirInfo {
+    public static class ReplicaLogDirInfo {
         // The current log directory of the replica of this partition on the given broker.
         // Null if no replica is not found for this partition on the given broker.
         private final String currentReplicaLogDir;

clients/src/main/java/org/apache/kafka/clients/admin/ElectLeadersOptions.java

@@ -28,5 +28,5 @@
  * The API of this class is evolving, see {@link Admin} for details.
  */
 @InterfaceStability.Evolving
-final public class ElectLeadersOptions extends AbstractOptions<ElectLeadersOptions> {
+public final class ElectLeadersOptions extends AbstractOptions<ElectLeadersOptions> {
 }

clients/src/main/java/org/apache/kafka/clients/admin/ElectLeadersResult.java

@@ -34,7 +34,7 @@
  * The API of this class is evolving, see {@link Admin} for details.
  */
 @InterfaceStability.Evolving
-final public class ElectLeadersResult {
+public final class ElectLeadersResult {
     private final KafkaFuture<Map<TopicPartition, Optional<Throwable>>> electionFuture;
 
     ElectLeadersResult(KafkaFuture<Map<TopicPartition, Optional<Throwable>>> electionFuture) {

clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java

@@ -3483,7 +3483,7 @@ private Set<AclOperation> validAclOperations(final int authorizedOperations) {
             .collect(Collectors.toSet());
     }
 
-    private final static class ListConsumerGroupsResults {
+    private static final class ListConsumerGroupsResults {
         private final List<Throwable> errors;
         private final HashMap<String, ConsumerGroupListing> listings;
         private final HashSet<Node> remaining;

clients/src/main/java/org/apache/kafka/clients/admin/TransactionState.java

@@ -34,7 +34,7 @@ public enum TransactionState {
     PREPARE_EPOCH_FENCE("PrepareEpochFence"),
     UNKNOWN("Unknown");
 
-    private final static Map<String, TransactionState> NAME_TO_ENUM = Arrays.stream(values())
+    private static final Map<String, TransactionState> NAME_TO_ENUM = Arrays.stream(values())
         .collect(Collectors.toMap(state -> state.name, Function.identity()));
 
     private final String name;

clients/src/main/java/org/apache/kafka/clients/admin/internals/AdminBootstrapAddresses.java

@@ -27,7 +27,7 @@
 import java.util.List;
 import java.util.Objects;
 
-final public class AdminBootstrapAddresses {
+public final class AdminBootstrapAddresses {
     private final boolean usingBootstrapControllers;
     private final List<InetSocketAddress> addresses;
 

clients/src/main/java/org/apache/kafka/clients/consumer/ConsumerGroupMetadata.java

@@ -26,10 +26,10 @@
  * Note: Any change to this class is considered public and requires a KIP.
  */
 public class ConsumerGroupMetadata {
-    final private String groupId;
-    final private int generationId;
-    final private String memberId;
-    final private Optional<String> groupInstanceId;
+    private final String groupId;
+    private final int generationId;
+    private final String memberId;
+    private final Optional<String> groupInstanceId;
 
     public ConsumerGroupMetadata(String groupId,
                                  int generationId,

clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java

@@ -523,7 +523,7 @@
  */
 public class KafkaConsumer<K, V> implements Consumer<K, V> {
 
-    private final static ConsumerDelegateCreator CREATOR = new ConsumerDelegateCreator();
+    private static final ConsumerDelegateCreator CREATOR = new ConsumerDelegateCreator();
 
     private final ConsumerDelegate<K, V> delegate;
 
@@ -1803,4 +1803,4 @@ KafkaConsumerMetrics kafkaConsumerMetrics() {
     boolean updateAssignmentMetadataIfNeeded(final Timer timer) {
         return delegate.updateAssignmentMetadataIfNeeded(timer);
     }
-}
+}

clients/src/main/java/org/apache/kafka/clients/consumer/KafkaShareConsumer.java

@@ -332,7 +332,7 @@
 @InterfaceStability.Evolving
 public class KafkaShareConsumer<K, V> implements ShareConsumer<K, V> {
 
-    private final static ShareConsumerDelegateCreator CREATOR = new ShareConsumerDelegateCreator();
+    private static final ShareConsumerDelegateCreator CREATOR = new ShareConsumerDelegateCreator();
 
     private final ShareConsumerDelegate<K, V> delegate;
 

clients/src/main/java/org/apache/kafka/clients/consumer/internals/AbstractStickyAssignor.java

@@ -85,7 +85,7 @@ public MemberData(List<TopicPartition> partitions, Optional<Integer> generation)
         }
     }
 
-    abstract protected MemberData memberData(Subscription subscription);
+    protected abstract MemberData memberData(Subscription subscription);
 
     @Override
     public Map<String, List<TopicPartition>> assignPartitions(Map<String, List<PartitionInfo>> partitionsPerTopic,

clients/src/main/java/org/apache/kafka/clients/consumer/internals/ConsumerCoordinator.java

@@ -96,7 +96,7 @@
  * This class manages the coordination process with the consumer coordinator.
  */
 public final class ConsumerCoordinator extends AbstractCoordinator {
-    private final static TopicPartitionComparator COMPARATOR = new TopicPartitionComparator();
+    private static final TopicPartitionComparator COMPARATOR = new TopicPartitionComparator();
 
     private final GroupRebalanceConfig rebalanceConfig;
     private final Logger log;

clients/src/main/java/org/apache/kafka/clients/consumer/internals/MembershipManagerImpl.java

@@ -118,13 +118,13 @@ public class MembershipManagerImpl implements MembershipManager {
     /**
      * TopicPartition comparator based on topic name and partition id.
      */
-    final static TopicPartitionComparator TOPIC_PARTITION_COMPARATOR = new TopicPartitionComparator();
+    static final TopicPartitionComparator TOPIC_PARTITION_COMPARATOR = new TopicPartitionComparator();
 
     /**
      * TopicIdPartition comparator based on topic name and partition id (ignoring ID while sorting,
      * as this is sorted mainly for logging purposes).
      */
-    final static TopicIdPartitionComparator TOPIC_ID_PARTITION_COMPARATOR = new TopicIdPartitionComparator();
+    static final TopicIdPartitionComparator TOPIC_ID_PARTITION_COMPARATOR = new TopicIdPartitionComparator();
 
     /**
      * Group ID of the consumer group the member will be part of, provided when creating the current

clients/src/main/java/org/apache/kafka/clients/consumer/internals/RequestState.java

@@ -24,8 +24,8 @@ class RequestState {
 
     private final Logger log;
     protected final String owner;
-    final static int RETRY_BACKOFF_EXP_BASE = 2;
-    final static double RETRY_BACKOFF_JITTER = 0.2;
+    static final int RETRY_BACKOFF_EXP_BASE = 2;
+    static final double RETRY_BACKOFF_JITTER = 0.2;
     protected final ExponentialBackoff exponentialBackoff;
     protected long lastSentMs = -1;
     protected long lastReceivedMs = -1;
@@ -159,4 +159,4 @@ protected String toStringBase() {
     public String toString() {
         return getClass().getSimpleName() + "{" + toStringBase() + '}';
     }
-}
+}

clients/src/main/java/org/apache/kafka/clients/consumer/internals/Utils.java

@@ -26,7 +26,7 @@
 
 public final class Utils {
 
-    final static class PartitionComparator implements Comparator<TopicPartition>, Serializable {
+    static final class PartitionComparator implements Comparator<TopicPartition>, Serializable {
         private static final long serialVersionUID = 1L;
         private final Map<String, List<String>> map;
 
@@ -46,7 +46,7 @@ public int compare(TopicPartition o1, TopicPartition o2) {
         }
     }
 
-    public final static class TopicPartitionComparator implements Comparator<TopicPartition>, Serializable {
+    public static final class TopicPartitionComparator implements Comparator<TopicPartition>, Serializable {
         private static final long serialVersionUID = 1L;
 
         @Override
@@ -62,7 +62,7 @@ public int compare(TopicPartition topicPartition1, TopicPartition topicPartition
         }
     }
 
-    public final static class TopicIdPartitionComparator implements Comparator<TopicIdPartition>, Serializable {
+    public static final class TopicIdPartitionComparator implements Comparator<TopicIdPartition>, Serializable {
         private static final long serialVersionUID = 1L;
 
         /**

clients/src/main/java/org/apache/kafka/clients/producer/internals/BuiltInPartitioner.java

@@ -45,7 +45,7 @@ public class BuiltInPartitioner {
     private final AtomicReference<StickyPartitionInfo> stickyPartitionInfo = new AtomicReference<>();
 
     // Visible and used for testing only.
-    static volatile public Supplier<Integer> mockRandom = null;
+    public static volatile Supplier<Integer> mockRandom = null;
 
     /**
      * BuiltInPartitioner constructor.
@@ -331,7 +331,7 @@ public static int partitionForKey(final byte[] serializedKey, final int numParti
     /**
      * The partition load stats for each topic that are used for adaptive partition distribution.
      */
-    private final static class PartitionLoadStats {
+    private static final class PartitionLoadStats {
         public final int[] cumulativeFrequencyTable;
         public final int[] partitionIds;
         public final int length;

clients/src/main/java/org/apache/kafka/clients/producer/internals/ProducerBatch.java

@@ -395,7 +395,7 @@ public boolean isCompressed() {
     /**
      * A callback and the associated FutureRecordMetadata argument to pass to it.
      */
-    final private static class Thunk {
+    private static final class Thunk {
         final Callback callback;
         final FutureRecordMetadata future;
 

clients/src/main/java/org/apache/kafka/clients/producer/internals/RecordAccumulator.java

@@ -1208,7 +1208,7 @@ public PartitionerConfig() {
     /*
      * Metadata about a record just appended to the record accumulator
      */
-    public final static class RecordAppendResult {
+    public static final class RecordAppendResult {
         public final FutureRecordMetadata future;
         public final boolean batchIsFull;
         public final boolean newBatchCreated;
@@ -1242,7 +1242,7 @@ public interface AppendCallbacks extends Callback {
     /*
      * The set of nodes that have at least one complete record batch in the accumulator
      */
-    public final static class ReadyCheckResult {
+    public static final class ReadyCheckResult {
         public final Set<Node> readyNodes;
         public final long nextReadyCheckDelayMs;
         public final Set<String> unknownLeaderTopics;
@@ -1270,9 +1270,9 @@ public TopicInfo(LogContext logContext, String topic, int stickyBatchSize) {
      * Node latency stats for each node that are used for adaptive partition distribution
      * Visible for testing
      */
-    public final static class NodeLatencyStats {
-        volatile public long readyTimeMs;  // last time the node had batches ready to send
-        volatile public long drainTimeMs;  // last time the node was able to drain batches
+    public static final class NodeLatencyStats {
+        public volatile long readyTimeMs;  // last time the node had batches ready to send
+        public volatile long drainTimeMs;  // last time the node was able to drain batches
 
         NodeLatencyStats(long nowMs) {
             readyTimeMs = nowMs;

clients/src/main/java/org/apache/kafka/clients/producer/internals/SenderMetricsRegistry.java

@@ -30,7 +30,7 @@
 
 public class SenderMetricsRegistry {
 
-    final static String TOPIC_METRIC_GROUP_NAME = "producer-topic-metrics";
+    static final String TOPIC_METRIC_GROUP_NAME = "producer-topic-metrics";
 
     private final List<MetricNameTemplate> allTemplates;
 

clients/src/main/java/org/apache/kafka/clients/producer/internals/TransactionManager.java

@@ -480,7 +480,7 @@ ProducerIdAndEpoch producerIdAndEpoch() {
         return producerIdAndEpoch;
     }
 
-    synchronized public void maybeUpdateProducerIdAndEpoch(TopicPartition topicPartition) {
+    public synchronized void maybeUpdateProducerIdAndEpoch(TopicPartition topicPartition) {
         if (hasFatalError()) {
             log.debug("Ignoring producer ID and epoch update request since the producer is in fatal error state");
             return;

clients/src/main/java/org/apache/kafka/common/ConsumerGroupState.java

@@ -36,7 +36,7 @@ public enum ConsumerGroupState {
     ASSIGNING("Assigning"),
     RECONCILING("Reconciling");
 
-    private final static Map<String, ConsumerGroupState> NAME_TO_ENUM = Arrays.stream(values())
+    private static final Map<String, ConsumerGroupState> NAME_TO_ENUM = Arrays.stream(values())
         .collect(Collectors.toMap(state -> state.name.toUpperCase(Locale.ROOT), Function.identity()));
 
     private final String name;

clients/src/main/java/org/apache/kafka/common/GroupType.java

@@ -27,7 +27,7 @@ public enum GroupType {
     CONSUMER("Consumer"),
     CLASSIC("Classic");
 
-    private final static Map<String, GroupType> NAME_TO_ENUM = Arrays.stream(values())
+    private static final Map<String, GroupType> NAME_TO_ENUM = Arrays.stream(values())
         .collect(Collectors.toMap(type -> type.name.toLowerCase(Locale.ROOT), Function.identity()));
 
     private final String name;

clients/src/main/java/org/apache/kafka/common/KafkaException.java

@@ -21,7 +21,7 @@
  */
 public class KafkaException extends RuntimeException {
 
-    private final static long serialVersionUID = 1L;
+    private static final long serialVersionUID = 1L;
 
     public KafkaException(String message, Throwable cause) {
         super(message, cause);

clients/src/main/java/org/apache/kafka/common/KafkaFuture.java

@@ -53,7 +53,7 @@ public interface BaseFunction<A, B> {
      * @deprecated Since Kafka 3.0. Use the {@link BaseFunction} functional interface.
      */
     @Deprecated
-    public static abstract class Function<A, B> implements BaseFunction<A, B> { }
+    public abstract static class Function<A, B> implements BaseFunction<A, B> { }
 
     /**
      * A consumer of two different types of object.

clients/src/main/java/org/apache/kafka/common/ShareGroupState.java

@@ -32,7 +32,7 @@ public enum ShareGroupState {
     DEAD("Dead"),
     EMPTY("Empty");
 
-    private final static Map<String, ShareGroupState> NAME_TO_ENUM = Arrays.stream(values())
+    private static final Map<String, ShareGroupState> NAME_TO_ENUM = Arrays.stream(values())
             .collect(Collectors.toMap(state -> state.name.toUpperCase(Locale.ROOT), Function.identity()));
 
     private final String name;

clients/src/main/java/org/apache/kafka/common/acl/AclOperation.java

@@ -121,7 +121,7 @@ public enum AclOperation {
     // Note: we cannot have more than 30 ACL operations without modifying the format used
     // to describe ACL operations in MetadataResponse.
 
-    private final static HashMap<Byte, AclOperation> CODE_TO_VALUE = new HashMap<>();
+    private static final HashMap<Byte, AclOperation> CODE_TO_VALUE = new HashMap<>();
 
     static {
         for (AclOperation operation : AclOperation.values()) {

clients/src/main/java/org/apache/kafka/common/acl/AclPermissionType.java

@@ -50,7 +50,7 @@ public enum AclPermissionType {
      */
     ALLOW((byte) 3);
 
-    private final static HashMap<Byte, AclPermissionType> CODE_TO_VALUE = new HashMap<>();
+    private static final HashMap<Byte, AclPermissionType> CODE_TO_VALUE = new HashMap<>();
 
     static {
         for (AclPermissionType permissionType : AclPermissionType.values()) {

clients/src/main/java/org/apache/kafka/common/config/internals/BrokerSecurityConfigs.java

@@ -112,7 +112,7 @@ public class BrokerSecurityConfigs {
     public static final String SSL_ALLOW_SAN_CHANGES_DOC = "Indicates whether changes to the certificate subject alternative names should be allowed during " +
             "a dynamic reconfiguration of certificates or not.";
 
-    public final static String SASL_MECHANISM_INTER_BROKER_PROTOCOL_CONFIG = "sasl.mechanism.inter.broker.protocol";
-    public final static String SASL_MECHANISM_INTER_BROKER_PROTOCOL_DOC = "SASL mechanism used for inter-broker communication. Default is GSSAPI.";
+    public static final String SASL_MECHANISM_INTER_BROKER_PROTOCOL_CONFIG = "sasl.mechanism.inter.broker.protocol";
+    public static final String SASL_MECHANISM_INTER_BROKER_PROTOCOL_DOC = "SASL mechanism used for inter-broker communication. Default is GSSAPI.";
 
 }

clients/src/main/java/org/apache/kafka/common/errors/TransactionAbortedException.java

@@ -22,7 +22,7 @@
  */
 public class TransactionAbortedException extends ApiException {
 
-    private final static long serialVersionUID = 1L;
+    private static final long serialVersionUID = 1L;
 
     public TransactionAbortedException(String message, Throwable cause) {
         super(message, cause);

clients/src/main/java/org/apache/kafka/common/internals/FatalExitError.java

@@ -27,7 +27,7 @@
  */
 public class FatalExitError extends Error {
 
-    private final static long serialVersionUID = 1L;
+    private static final long serialVersionUID = 1L;
 
     private final int statusCode;
 

clients/src/main/java/org/apache/kafka/common/protocol/types/Schema.java

@@ -25,7 +25,7 @@
  * The schema for a compound record definition
  */
 public class Schema extends Type {
-    private final static Object[] NO_VALUES = new Object[0];
+    private static final Object[] NO_VALUES = new Object[0];
 
     private final BoundField[] fields;
     private final Map<String, BoundField> fieldsByName;
@@ -229,7 +229,7 @@ private static void handleNode(Type node, Visitor visitor) {
     /**
      * Override one or more of the visit methods with the desired logic.
      */
-    public static abstract class Visitor {
+    public abstract static class Visitor {
         public void visit(Schema schema) {}
         public void visit(Type field) {}
     }

clients/src/main/java/org/apache/kafka/common/protocol/types/Type.java

@@ -82,7 +82,7 @@ public final boolean isArray() {
     /**
      * A Type that can return its description for documentation purposes.
      */
-    public static abstract class DocumentedType extends Type {
+    public abstract static class DocumentedType extends Type {
 
         /**
          * Short name of the type to identify it in documentation;