Code cleanup (#1461)

* Code cleanup

* Fix flux tests

* Fix checkstyle errors

* Fix compile error

hexagonal/src/main/java/com/iluwatar/hexagonal/banking/InMemoryBank.java

@@ -32,7 +32,7 @@ import java.util.Map;
  */
 public class InMemoryBank implements WireTransfers {
 
-  private static Map<String, Integer> accounts = new HashMap<>();
+  private static final Map<String, Integer> accounts = new HashMap<>();
 
   static {
     accounts

hexagonal/src/main/java/com/iluwatar/hexagonal/database/InMemoryTicketRepository.java

@@ -34,7 +34,7 @@ import java.util.Optional;
  */
 public class InMemoryTicketRepository implements LotteryTicketRepository {
 
-  private static Map<LotteryTicketId, LotteryTicket> tickets = new HashMap<>();
+  private static final Map<LotteryTicketId, LotteryTicket> tickets = new HashMap<>();
 
   @Override
   public Optional<LotteryTicket> findById(LotteryTicketId id) {

hexagonal/src/main/java/com/iluwatar/hexagonal/domain/LotteryNumbers.java

@@ -116,7 +116,7 @@ public class LotteryNumbers {
    */
   private static class RandomNumberGenerator {
 
-    private PrimitiveIterator.OfInt randomIterator;
+    private final PrimitiveIterator.OfInt randomIterator;
 
     /**
      * Initialize a new random number generator that generates random numbers in the range [min,

hexagonal/src/main/java/com/iluwatar/hexagonal/domain/LotteryTicketId.java

@@ -30,7 +30,7 @@ import java.util.concurrent.atomic.AtomicInteger;
  */
 public class LotteryTicketId {
 
-  private static AtomicInteger numAllocated = new AtomicInteger(0);
+  private static final AtomicInteger numAllocated = new AtomicInteger(0);
   private final int id;
 
   public LotteryTicketId() {

hexagonal/src/main/java/com/iluwatar/hexagonal/eventlog/MongoEventLog.java

@@ -41,7 +41,7 @@ public class MongoEventLog implements LotteryEventLog {
   private MongoDatabase database;
   private MongoCollection<Document> eventsCollection;
 
-  private StdOutEventLog stdOutEventLog = new StdOutEventLog();
+  private final StdOutEventLog stdOutEventLog = new StdOutEventLog();
 
   /**
    * Constructor.

hexagonal/src/test/java/com/iluwatar/hexagonal/domain/LotteryTest.java

@@ -43,7 +43,7 @@ import org.junit.jupiter.api.Test;
  */
 class LotteryTest {
 
-  private Injector injector;
+  private final Injector injector;
   @Inject
   private LotteryAdministration administration;
   @Inject