fix: clean up imports and use Set.copyOf for snapshot in fullyRefreshCache

Agent-Logs-Url: https://github.com/kubernetes-client/java/sessions/07e0048a-55b8-42c1-809c-ff20e3bd4837

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Author: Copilot

spring/src/main/java/io/kubernetes/client/spring/extended/manifests/KubernetesFromConfigMapProcessor.java

@@ -20,6 +20,7 @@
 import io.kubernetes.client.spring.extended.manifests.configmaps.ConfigMapGetter;
 import java.lang.reflect.Field;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
@@ -104,9 +105,8 @@ private static void fullyRefreshCache(
     // TODO: make the cache data refreshment atomic
     Map<String, String> newData = configMap.getData();
     newData.forEach(configMapDataCache::put);
-    configMapDataCache.asMap().keySet().stream()
+    Set.copyOf(configMapDataCache.asMap().keySet()).stream()
         .filter(key -> !newData.containsKey(key))
-        .collect(java.util.stream.Collectors.toList())
         .forEach(configMapDataCache::invalidate);
   }