Fixed checkStyle and ErrorProne warns

mapdb_storage/src/main/java/io/moquette/persistence/mapdb/MapDBMessagesStore.java

@@ -78,7 +78,7 @@ class MapDBMessagesStore implements IMessagesStore {
     public void storeRetained(Topic topic, StoredMessage storedMessage) {
         LOG.debug("Store retained message for topic={}, CId={}", topic, storedMessage.getClientID());
         if (storedMessage.getClientID() == null) {
-            throw new IllegalArgumentException( "Message to be persisted must have a not null client ID");
+            throw new IllegalArgumentException("Message to be persisted must have a not null client ID");
         }
         m_retainedStore.put(topic, storedMessage);
     }

mapdb_storage/src/main/java/io/moquette/persistence/mapdb/MapDBPersistentStore.java

@@ -63,6 +63,7 @@ public class MapDBPersistentStore implements IStore {
         return m_sessionsStore;
     }
 
+    @SuppressWarnings("FutureReturnValueIgnored")
     @Override
     public void initStore() {
         LOG.info("Initializing MapDB store");

mapdb_storage/src/main/java/io/moquette/persistence/mapdb/MapDBSessionsStore.java

@@ -127,10 +127,12 @@ class MapDBSessionsStore implements ISessionsStore, ISubscriptionsStore {
     }
 
     @Override
-    public Subscription reload(Subscription subcription) {
-        ConcurrentMap<Topic, Subscription> clientSubscriptions = m_db.getHashMap("subscriptions_" + subcription.getClientId());
-        LOG.debug("Retrieving subscriptions. CId={}, subscriptions={}", subcription.getClientId(), clientSubscriptions);
-        return clientSubscriptions.get(subcription.getTopicFilter());
+    public Subscription reload(Subscription subscription) {
+        final String clientId = subscription.getClientId();
+        final String clientSubcMapName = "subscriptions_" + clientId;
+        ConcurrentMap<Topic, Subscription> clientSubscriptions = m_db.getHashMap(clientSubcMapName);
+        LOG.debug("Retrieving subscriptions. CId={}, subscriptions={}", clientId, clientSubscriptions);
+        return clientSubscriptions.get(subscription.getTopicFilter());
     }
 
     @Override
@@ -178,7 +180,6 @@ class MapDBSessionsStore implements ISessionsStore, ISubscriptionsStore {
             inFlightForClient.add(nextPacketId);
             this.m_inFlightIds.put(clientID, inFlightForClient);
             return nextPacketId;
-
         }
 
         int maxId = inFlightForClient.isEmpty() ? 0 : Collections.max(inFlightForClient);
@@ -264,7 +265,8 @@ class MapDBSessionsStore implements ISessionsStore, ISubscriptionsStore {
     @Override
     public int getInflightMessagesNo(String clientID) {
         int totalInflight = 0;
-        ConcurrentMap<Integer, StoredMessage> inflightPerClient = m_db.getHashMap(inboundMessageId2MessagesMapName(clientID));
+        final String infligthMessageMapName = inboundMessageId2MessagesMapName(clientID);
+        ConcurrentMap<Integer, StoredMessage> inflightPerClient = m_db.getHashMap(infligthMessageMapName);
         if (inflightPerClient != null) {
             totalInflight += inflightPerClient.size();
         }

mapdb_storage/src/test/java/io/moquette/persistence/mapdb/MapDBPersistentStoreTest.java

@@ -28,11 +28,13 @@ import org.junit.Before;
 import org.junit.Test;
 
 import java.io.File;
+import java.nio.charset.StandardCharsets;
 import java.util.Properties;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.*;
 
 /**
@@ -99,7 +101,7 @@ public class MapDBPersistentStoreTest extends MessageStoreTCK {
 
     @Test
     public void testNextPacketID() {
-        StoredMessage msgStored = new StoredMessage("Hello".getBytes(), MqttQoS.AT_LEAST_ONCE, "/topic");
+        StoredMessage msgStored = new StoredMessage("Hello".getBytes(UTF_8), MqttQoS.AT_LEAST_ONCE, "/topic");
         msgStored.setClientID(TEST_CLIENT);
 
         // request a first ID

mapdb_storage/src/test/java/io/moquette/persistence/mapdb/MapDBSessionsStoreTest.java

@@ -98,7 +98,8 @@ public class MapDBSessionsStoreTest {
     }
 
     @Test
-    public void testRetrieve1000ExpiredSessionPerformance() throws InterruptedException, ExecutionException, TimeoutException {
+    public void testRetrieve1000ExpiredSessionPerformance() throws InterruptedException, ExecutionException,
+                TimeoutException {
         MapDBSessionsStore sessionsStore = (MapDBSessionsStore) storageService.sessionsStore();
 
         final ExecutorService executorService = Executors.newFixedThreadPool(2);