Checkstyle class-design cleanup: add private utility ctors, mark final, drop redundant modifiers, add missing @Override

datastream-client/src/main/java/com/linkedin/datastream/BaseRestClientFactory.java

@@ -152,7 +152,7 @@ private static String getKey(String uri, Map<String, Object> httpConfig) {
    * shutdown, hence it is okay for us to make the threads daemon.
    */
   private class DaemonNamedThreadFactory extends NamedThreadFactory {
-    public DaemonNamedThreadFactory(String name) {
+    DaemonNamedThreadFactory(String name) {
       super(name + " " + StringUtils.substringAfterLast(_logger.getName(), "."));
     }
 

datastream-client/src/main/java/com/linkedin/datastream/DatastreamRestClientFactory.java

@@ -23,6 +23,10 @@
  * DatastreamRestClient, without doing a major refactoring of the code.
  */
 public final class DatastreamRestClientFactory {
+
+  private DatastreamRestClientFactory() {
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(DatastreamRestClientFactory.class);
   private static final BaseRestClientFactory<DatastreamRestClient> FACTORY =
       new BaseRestClientFactory<>(DatastreamRestClient.class, LOG);

datastream-client/src/main/java/com/linkedin/diagnostics/ServerComponentHealthRestClientFactory.java

@@ -21,6 +21,10 @@
  * Factory class for obtaining {@link ServerComponentHealthRestClient} objects.
  */
 public final class ServerComponentHealthRestClientFactory {
+
+  private ServerComponentHealthRestClientFactory() {
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(DatastreamRestClientFactory.class);
   private static final BaseRestClientFactory<ServerComponentHealthRestClient> FACTORY =
       new BaseRestClientFactory<>(ServerComponentHealthRestClient.class, LOG);

datastream-common/src/main/java/com/linkedin/datastream/common/AvroMessageEncoderUtil.java

@@ -25,7 +25,11 @@
 /**
  * Utility class to simplify Avro message encoding
  */
-public class AvroMessageEncoderUtil {
+public final class AvroMessageEncoderUtil {
+
+  private AvroMessageEncoderUtil() {
+  }
+
   public static final byte MAGIC_BYTE = 0x0;
 
   /**

datastream-common/src/main/java/com/linkedin/datastream/common/BrooklinEnvelopeMetadataConstants.java

@@ -8,7 +8,10 @@
 /**
  * Constants used in the metadata field of {@link BrooklinEnvelope}
  */
-public class BrooklinEnvelopeMetadataConstants {
+public final class BrooklinEnvelopeMetadataConstants {
+
+  private BrooklinEnvelopeMetadataConstants() {
+  }
 
   /**
    * Codes to identify the different data change operations

datastream-common/src/main/java/com/linkedin/datastream/common/DatastreamMetadataConstants.java

@@ -8,7 +8,10 @@
 /**
  * Various well known config keys used in datastream metadata.
  */
-public class DatastreamMetadataConstants {
+public final class DatastreamMetadataConstants {
+
+  private DatastreamMetadataConstants() {
+  }
 
   /**
    * Represents whether the datastream has an User managed destination (a.k.a BYOT - Bring your own topic)

datastream-common/src/main/java/com/linkedin/datastream/common/JsonUtils.java

@@ -32,6 +32,10 @@
  * for checking the
  */
 public final class JsonUtils {
+
+  private JsonUtils() {
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(JsonUtils.class.getName());
 
   private static final ObjectMapper MAPPER = new ObjectMapper();

datastream-common/src/main/java/com/linkedin/datastream/common/ReflectionUtils.java

@@ -18,7 +18,11 @@
 /**
  * Utility class to simplify usage of Java reflection.
  */
-public class ReflectionUtils {
+public final class ReflectionUtils {
+
+  private ReflectionUtils() {
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(ReflectionUtils.class);
 
   private static final Class<?>[][] COMPATIBLE_TYPES = {

datastream-common/src/main/java/com/linkedin/datastream/common/databases/dbreader/DatabaseChunkedReaderMetrics.java

@@ -52,7 +52,7 @@ class DatabaseChunkedReaderMetrics extends BrooklinMetrics {
    * @param source Aggregate metrics for source .i.e. at the Database table level
    * @param key Metrics at the reader level, identified by key
    */
-  public DatabaseChunkedReaderMetrics(String source, String key) {
+  DatabaseChunkedReaderMetrics(String source, String key) {
     super(CLASS_NAME, key);
     _source = source;
 

datastream-common/src/main/java/com/linkedin/datastream/connectors/CommonConnectorMetrics.java

@@ -68,7 +68,7 @@ static class EventProcMetrics extends BrooklinMetrics {
     final Meter _aggregatedErrorRate;
     final Meter _aggregatedProcessingAboveThreshold;
 
-    public EventProcMetrics(String className, String key) {
+    EventProcMetrics(String className, String key) {
       super(className, key);
       _lastEventReceivedTime = Instant.now();
       _eventsProcessedRate = DYNAMIC_METRICS_MANAGER.registerMetric(_className, _key, EVENTS_PROCESSED_RATE,
@@ -139,7 +139,7 @@ static class PollMetrics extends BrooklinMetrics {
     final Counter _aggregatedClientPollOverTimeout;
     final Counter _aggregatedClientPollIntervalOverSessionTimeout;
 
-    public PollMetrics(String className, String key) {
+    PollMetrics(String className, String key) {
       super(className, key);
       _numPolls = DYNAMIC_METRICS_MANAGER.registerMetric(_className, _key, NUM_POLLS, Meter.class);
       _eventCountsPerPoll = DYNAMIC_METRICS_MANAGER.registerMetric(_className, _key, EVENT_COUNTS_PER_POLL,
@@ -203,7 +203,7 @@ static class PartitionMetrics extends BrooklinMetrics {
     private final AtomicLong _numPartitions;
     private final AtomicLong _numStuckPartitions;
 
-    public PartitionMetrics(String className, String key) {
+    PartitionMetrics(String className, String key) {
       super(className, key);
       _fullMetricsKey = MetricRegistry.name(_className, _key);
       _rebalanceRate = DYNAMIC_METRICS_MANAGER.registerMetric(_className, _key, REBALANCE_RATE, Meter.class);

datastream-common/src/main/java/com/linkedin/datastream/kafka/KafkaDatastreamMetadataConstants.java

@@ -8,7 +8,10 @@
 /**
  * Metadata constants that are specific to Kafka (or Kafka MirrorMaker) datastreams.
  */
-public class KafkaDatastreamMetadataConstants {
+public final class KafkaDatastreamMetadataConstants {
+
+  private KafkaDatastreamMetadataConstants() {
+  }
 
   // Can be used by the transport provider to send to a particular Kafka cluster
   public static final String DESTINATION_KAFKA_BROKERS = "system.destination.KafkaBrokers";

datastream-common/src/main/java/com/linkedin/datastream/metrics/DynamicMetricsManager.java

@@ -28,7 +28,7 @@
 /**
  * Manages dynamic metrics and supports creating/updating metrics on the fly.
  */
-public class DynamicMetricsManager {
+public final class DynamicMetricsManager {
   static final String NO_KEY_PLACEHOLDER = "NO_KEY";
   private static final Logger LOG = LoggerFactory.getLogger(DynamicMetricsManager.class);
   private static DynamicMetricsManager _instance = null;

datastream-common/src/main/java/com/linkedin/datastream/metrics/JmxReporterFactory.java

@@ -21,7 +21,11 @@
  * A factory for {@link JmxReporter} objects that generates metrics whose
  * names are decided according to {@link BrooklinObjectNameFactory}.
  */
-public class JmxReporterFactory {
+public final class JmxReporterFactory {
+
+  private JmxReporterFactory() {
+  }
+
   private static final ObjectNameFactory OBJECT_NAME_FACTORY = new BrooklinObjectNameFactory();
 
   /**

datastream-common/src/main/java/com/linkedin/datastream/metrics/ResettableGauge.java

@@ -18,10 +18,10 @@
 class ResettableGauge<T> implements Gauge<T> {
   private Supplier<T> _supplier;
 
-  public ResettableGauge() {
+  ResettableGauge() {
   }
 
-  public ResettableGauge(Supplier<T> supplier) {
+  ResettableGauge(Supplier<T> supplier) {
     _supplier = supplier;
   }
 

datastream-file-connector/src/main/java/com/linkedin/datastream/connectors/file/FileProcessor.java

@@ -50,7 +50,7 @@ class FileProcessor implements Runnable {
   private boolean _cancelRequested;
   private boolean _isStopped;
 
-  public FileProcessor(DatastreamTask datastreamTask, DatastreamEventProducer producer) throws FileNotFoundException {
+  FileProcessor(DatastreamTask datastreamTask, DatastreamEventProducer producer) throws FileNotFoundException {
     _task = datastreamTask;
     _fileName = datastreamTask.getDatastreamSource().getConnectionString();
     _positionKey = new FilePositionKey(_task.getTaskPrefix(), _task.getDatastreamTaskName(), Instant.now(), _fileName);

datastream-kafka-connector/src/main/java/com/linkedin/datastream/connectors/kafka/AbstractKafkaConnector.java

@@ -789,6 +789,7 @@ public Map<String, Map<Integer, Long>> getConsumptionLagForTask(DatastreamTask t
   /**
    * {@inheritDoc}
    */
+  @Override
   public List<String> getActiveTasks() {
     List<DatastreamTask> tasks = new ArrayList<>();
 

datastream-kafka-connector/src/main/java/com/linkedin/datastream/connectors/kafka/KafkaConnectorDiagUtils.java

@@ -22,7 +22,11 @@
 /**
  * Utility class for Kafka based connectors
  */
-public class KafkaConnectorDiagUtils {
+public final class KafkaConnectorDiagUtils {
+
+  private KafkaConnectorDiagUtils() {
+  }
+
   /**
    * Reduce/Merge the KafkaTopicPartitionStatsResponse responses of a collection of host/instance into one response
    */

datastream-kafka-connector/src/main/java/com/linkedin/datastream/connectors/kafka/mirrormaker/KafkaMirrorMakerConnector.java

@@ -268,7 +268,7 @@ private void validateSourceConnectionString(Datastream stream) throws Datastream
    *  PartitionDiscoveryThread listens to Kafka partitions periodically using the _consumer.listTopic()
    *  to fetch the latest subscribed partitions for a given datastreamGroup
    */
-  class PartitionDiscoveryThread extends Thread {
+  final class PartitionDiscoveryThread extends Thread {
     // The datastream group that this partitionDiscoveryThread is responsible to handle
     private final DatastreamGroup _datastreamGroup;
 

datastream-kafka-connector/src/main/java/com/linkedin/datastream/connectors/kafka/mirrormaker/KafkaMirrorMakerDatastreamMetadata.java

@@ -15,6 +15,9 @@
  */
 public final class KafkaMirrorMakerDatastreamMetadata {
 
+  private KafkaMirrorMakerDatastreamMetadata() {
+  }
+
   public static final String IDENTITY_PARTITIONING_ENABLED = "system.destination.identityPartitioningEnabled";
 
   /**

datastream-kafka/src/main/java/com/linkedin/datastream/kafka/KafkaTransportProviderUtils.java

@@ -17,7 +17,11 @@
 /**
  * Utility methods for {@link KafkaTransportProvider}
  */
-public class KafkaTransportProviderUtils {
+public final class KafkaTransportProviderUtils {
+
+  private KafkaTransportProviderUtils() {
+  }
+
   private static final Logger LOG = LoggerFactory.getLogger(KafkaTransportProviderUtils.class.getName());
   // Mapping destination URI to topic name
   private final static Map<String, String> URI_TOPICS = new ConcurrentHashMap<>();

datastream-server/src/main/java/com/linkedin/datastream/server/Coordinator.java

@@ -2482,7 +2482,7 @@ private static class CoordinatorMetrics {
     private final List<BrooklinMetricInfo> _metricInfos;
     private final DynamicMetricsManager _dynamicMetricsManager;
 
-    public CoordinatorMetrics(Coordinator coordinator) {
+    CoordinatorMetrics(Coordinator coordinator) {
       _coordinator = coordinator;
       _metricInfos = new ArrayList<>();
       _dynamicMetricsManager = DynamicMetricsManager.getInstance();

datastream-server/src/main/java/com/linkedin/datastream/server/DatastreamServerConfigurationConstants.java

@@ -10,6 +10,9 @@
  */
 public final class DatastreamServerConfigurationConstants {
 
+  private DatastreamServerConfigurationConstants() {
+  }
+
   public static final String CONFIG_PREFIX = "brooklin.server.";
   public static final String CONFIG_CONNECTOR_NAMES = CONFIG_PREFIX + "connectorNames";
   public static final String CONFIG_HTTP_PORT = CONFIG_PREFIX + "httpPort";

datastream-server/src/main/java/com/linkedin/datastream/server/assignment/StickyPartitionAssignmentStrategy.java

@@ -778,7 +778,7 @@ private static class ElasticTaskAssignmentInfo {
     private final int _actualPartitionsPerTask;
     private final boolean _needsAdjustment;
 
-    public ElasticTaskAssignmentInfo(int actualPartitionsPerTask, boolean needsAdjustment) {
+    ElasticTaskAssignmentInfo(int actualPartitionsPerTask, boolean needsAdjustment) {
       _actualPartitionsPerTask = actualPartitionsPerTask;
       _needsAdjustment = needsAdjustment;
     }

datastream-server/src/main/java/com/linkedin/datastream/server/zk/ZkAdapter.java

@@ -1699,7 +1699,7 @@ private class ZkBackedDMSDatastreamList implements IZkChildListener, IZkDataList
     /**
      * Sets up a watch on the {@code /{cluster}/dms} tree, so it can be notified of future changes.
      */
-    public ZkBackedDMSDatastreamList() {
+    ZkBackedDMSDatastreamList() {
       _path = KeyBuilder.datastreams(_cluster);
       _zkclient.ensurePath(KeyBuilder.datastreams(_cluster));
       LOG.info("ZkBackedDMSDatastreamList::Subscribing to the changes under the path " + _path);
@@ -1768,7 +1768,7 @@ private class ZkBackedLiveInstanceListProvider implements IZkChildListener {
      * Sets up a watch on the {@code /{cluster}/liveinstances} tree, so it can be notified
      * of future changes.
      */
-    public ZkBackedLiveInstanceListProvider() {
+    ZkBackedLiveInstanceListProvider() {
       _path = KeyBuilder.liveInstances(_cluster);
       _zkclient.ensurePath(_path);
       LOG.info("ZkBackedLiveInstanceListProvider::Subscribing to the under the path " + _path);
@@ -1850,7 +1850,7 @@ private class ZkBackedTaskListProvider implements IZkChildListener, IZkDataListe
      * Constructor
      * @param instanceName Instance for which the datastream task assignment is to be watched.
      */
-    public ZkBackedTaskListProvider(String cluster, String instanceName) {
+    ZkBackedTaskListProvider(String cluster, String instanceName) {
       _path = KeyBuilder.instanceAssignments(cluster, instanceName);
       LOG.info("ZkBackedTaskListProvider::Subscribing to the changes under the path " + _path);
       _zkclient.subscribeChildChanges(_path, this);
@@ -1901,7 +1901,7 @@ private class ZkTargetAssignmentProvider implements IZkDataListener {
     /**
      * Constructor
      */
-    public ZkTargetAssignmentProvider(Set<String> connectorTypes) {
+    ZkTargetAssignmentProvider(Set<String> connectorTypes) {
       for (String connectorType : connectorTypes) {
         String path = KeyBuilder.getTargetAssignmentBase(_cluster, connectorType);
         _zkclient.subscribeDataChanges(path, this);
@@ -1956,7 +1956,7 @@ private class ZkStateChangeListener implements IZkStateListener {
         new ThreadFactoryBuilder().setDaemon(true).setNameFormat("SessionExpiryScheduler-%d").build());
     private Future<?> _zkSessionExpiryFuture = CompletableFuture.completedFuture("completed");
 
-    public ZkStateChangeListener() {
+    ZkStateChangeListener() {
       _zkclient.subscribeStateChanges(this);
     }
 

datastream-testcommon/src/main/java/com/linkedin/datastream/server/EmbeddedDatastreamCluster.java

@@ -28,7 +28,7 @@
 /**
  * Provides a Datastream cluster, including a ZooKeeper cluster and Kafka cluster (if necessary), for testing purposes.
  */
-public class EmbeddedDatastreamCluster {
+public final class EmbeddedDatastreamCluster {
 
   public static final String CONFIG_ZK_CONNECT = "zookeeper.connect";
   public static final String BOOTSTRAP_SERVERS_CONFIG = "bootstrap.servers";

datastream-testcommon/src/main/java/com/linkedin/datastream/testutil/DatastreamTestUtils.java

@@ -27,7 +27,11 @@
 /**
  * Utility class for writing tests that deal with Datastream objects.
  */
-public class DatastreamTestUtils {
+public final class DatastreamTestUtils {
+
+  private DatastreamTestUtils() {
+  }
+
   /**
    * Creates variable number of Datastreams from a list of names with
    * fields populated with default values except for name and connector type.

datastream-testcommon/src/main/java/com/linkedin/datastream/testutil/MetricsTestUtils.java

@@ -35,7 +35,7 @@
  * Test utilities for verifying metrics
  * @see MetricsAware
  */
-public class MetricsTestUtils {
+public final class MetricsTestUtils {
   // Mapping of BrooklinMetricInfo sub-types -> com.codahale.metrics types
   private static final Map<Class<? extends BrooklinMetricInfo>, Class<? extends Metric>> METRICS_TYPE_MAPPING = ImmutableMap.of(
       BrooklinCounterInfo.class, Counter.class,

datastream-tools/src/main/java/com/linkedin/datastream/tools/DatastreamRestClientCli.java

@@ -35,7 +35,7 @@
 /**
  * The main class containing the entry point of the Datastream REST client command line utility
  */
-public class DatastreamRestClientCli {
+public final class DatastreamRestClientCli {
 
   private DatastreamRestClientCli() {
   }

datastream-tools/src/main/java/com/linkedin/datastream/tools/OptionConstants.java

@@ -8,7 +8,10 @@
 /**
  * String constants for options used with {@link DatastreamRestClientCli}
  */
-public class OptionConstants {
+public final class OptionConstants {
+
+  private OptionConstants() {
+  }
 
   public static final String OPT_SHORT_MGMT_URI = "u";
   public static final String OPT_LONG_MGMT_URI = "uri";

datastream-tools/src/main/java/com/linkedin/datastream/tools/OptionUtils.java

@@ -11,7 +11,10 @@
 /**
  * Utility class for creating command line {@link Option}s
  */
-public class OptionUtils {
+public final class OptionUtils {
+
+  private OptionUtils() {
+  }
 
   /**
    * Create a command line option

datastream-utils/src/main/java/com/linkedin/datastream/common/AvroUtils.java

@@ -31,7 +31,10 @@
 /**
  * Utility methods for encoding/decoding data into/from Avro.
  */
-public class AvroUtils {
+public final class AvroUtils {
+
+  private AvroUtils() {
+  }
 
   /**
    * Encode an Avro record into byte array

datastream-utils/src/main/java/com/linkedin/datastream/common/FileUtils.java

@@ -17,7 +17,10 @@
 /**
  * Class that contains the helper utility methods for File system operations.
  */
-public class FileUtils {
+public final class FileUtils {
+
+  private FileUtils() {
+  }
 
   private static final Logger LOG = LoggerFactory.getLogger(FileUtils.class.getName());