Set constants private and final

bubble-server/src/main/java/bubble/dao/device/DeviceDAO.java

@@ -31,10 +31,9 @@ import static org.cobbzilla.util.reflect.ReflectionUtil.copy;
 @Repository @Slf4j
 public class DeviceDAO extends AccountOwnedEntityDAO<Device> {
 
-    public static final File VPN_REFRESH_USERS_FILE = new File(HOME_DIR, ".algo_refresh_users");
-
-    private static short SPARE_DEVICES_PER_ACCOUNT_MAX = 10;
-    private static short SPARE_DEVICES_PER_ACCOUNT_THRESHOLD = 5;
+    private static final File VPN_REFRESH_USERS_FILE = new File(HOME_DIR, ".algo_refresh_users");
+    private static final short SPARE_DEVICES_PER_ACCOUNT_MAX = 10;
+    private static final short SPARE_DEVICES_PER_ACCOUNT_THRESHOLD = 5;
 
     @Autowired private BubbleConfiguration configuration;
     @Autowired private AppDataDAO dataDAO;