diff --git a/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ContentCluster.java b/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ContentCluster.java
index c0710a2898f7..7192bc681d35 100644
--- a/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ContentCluster.java
+++ b/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/ContentCluster.java
@@ -19,7 +19,7 @@
 import static com.yahoo.vdslib.state.NodeState.ORCHESTRATOR_RESERVED_DESCRIPTION;
 import static com.yahoo.vespa.clustercontroller.core.NodeStateChangeChecker.Result;
 
-public class ContentCluster {
+public final class ContentCluster {
 
     private static final int pollingFrequency = 5000;
 
diff --git a/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/MasterDataGatherer.java b/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/MasterDataGatherer.java
index 3f6c494a3623..91625e64472c 100644
--- a/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/MasterDataGatherer.java
+++ b/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/database/MasterDataGatherer.java
@@ -1,16 +1,23 @@
 // Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.clustercontroller.core.database;
 
+import org.apache.zookeeper.AsyncCallback;
+import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.WatchedEvent;
+import org.apache.zookeeper.Watcher;
+import org.apache.zookeeper.ZooKeeper;
 import org.apache.zookeeper.data.Stat;
-import org.apache.zookeeper.*;
 
 import java.nio.charset.StandardCharsets;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
 import java.util.logging.Logger;
-import java.util.*;
 
 import java.util.logging.Level;
 
-public class MasterDataGatherer {
+public final class MasterDataGatherer {
 
     private static final Logger log = Logger.getLogger(MasterDataGatherer.class.getName());
 
diff --git a/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/restapiv2/Response.java b/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/restapiv2/Response.java
index 7af5f93fa219..ec6bf5045ed6 100644
--- a/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/restapiv2/Response.java
+++ b/clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/restapiv2/Response.java
@@ -32,16 +32,16 @@ public UnitStateImpl(NodeState ns) throws StateRestApiException {
             this.reason = ns.getDescription();
         }
 
-        public String parseId(State id) throws StateRestApiException {
-            switch (id) {
-                case UP: return "up";
-                case DOWN: return "down";
-                case INITIALIZING: return "initializing";
-                case MAINTENANCE: return "maintenance";
-                case RETIRED: return "retired";
-                case STOPPING: return "stopping";
-            }
-            throw new InternalFailure("Unknown state '" + id + "' found.");
+        public static String parseId(State id) throws StateRestApiException {
+            return switch (id) {
+                case UP -> "up";
+                case DOWN -> "down";
+                case INITIALIZING -> "initializing";
+                case MAINTENANCE -> "maintenance";
+                case RETIRED -> "retired";
+                case STOPPING -> "stopping";
+                default -> throw new InternalFailure("Unknown state '" + id + "' found.");
+            };
         }
 
         @Override