Make field final

Author: adutra

core/src/main/java/com/datastax/oss/driver/internal/core/time/AtomicTimestampGenerator.java

@@ -46,7 +46,7 @@
 @ThreadSafe
 public class AtomicTimestampGenerator extends MonotonicTimestampGenerator {
 
-  private AtomicLong lastRef = new AtomicLong(0);
+  private final AtomicLong lastRef = new AtomicLong(0);
 
   public AtomicTimestampGenerator(DriverContext context) {
     super(context);

core/src/main/java/com/datastax/oss/driver/internal/core/util/DefaultDependencyChecker.java

@@ -28,7 +28,7 @@ public class DefaultDependencyChecker {
 
   private static final Logger LOG = LoggerFactory.getLogger(DefaultDependencyChecker.class);
 
-  private static ConcurrentHashMap<Dependency, Boolean> CACHE = new ConcurrentHashMap<>();
+  private static final ConcurrentHashMap<Dependency, Boolean> CACHE = new ConcurrentHashMap<>();
 
   /**
    * Return true iff we can find all classes for the dependency on the classpath, false otherwise