diff --git a/src/main/java/eirb/pg203/weather/data/api/WeatherDataCache.java b/src/main/java/eirb/pg203/weather/data/api/WeatherDataCache.java
index 88381b7..429cfcf 100644
--- a/src/main/java/eirb/pg203/weather/data/api/WeatherDataCache.java
+++ b/src/main/java/eirb/pg203/weather/data/api/WeatherDataCache.java
@@ -2,7 +2,6 @@ package eirb.pg203.weather.data.api;
 import eirb.pg203.weather.data.WeatherData;
 
 import java.time.Instant;
-import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Locale;
 
@@ -60,7 +59,7 @@ public class WeatherDataCache {
     }
   }
 
-  private HashMap<String, CacheValue> cache = new HashMap<>();
+  private final HashMap<String, CacheValue> cache = new HashMap<>();
   private static final long cacheTTL = 3600;  // Cache data Time To Live in sec
 
 	private String makeKey(String cityName, int day) {
diff --git a/src/test/java/eirb/pg203/weather/data/WeatherDataTest.java b/src/test/java/eirb/pg203/weather/data/WeatherDataTest.java
index c664abd..7e6c5e2 100644
--- a/src/test/java/eirb/pg203/weather/data/WeatherDataTest.java
+++ b/src/test/java/eirb/pg203/weather/data/WeatherDataTest.java
@@ -11,10 +11,7 @@ import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.EnumSource;
 import org.junit.jupiter.params.provider.MethodSource;
 
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 import java.time.Instant;
-import java.util.ArrayList;
 import java.util.stream.Stream;
 
 public class WeatherDataTest {