Collections.emptyXXX + Collections.singletonXXX => List/Set/Map.of

48 files changed, 136 insertions, 177 deletions

diff --git a/config-model/src/main/java/com/yahoo/config/model/ConfigModelRegistry.java b/config-model/src/main/java/com/yahoo/config/model/ConfigModelRegistry.java
index 51bd01de5bc..f25f130eed0 100644
--- a/config-model/src/main/java/com/yahoo/config/model/ConfigModelRegistry.java
+++ b/config-model/src/main/java/com/yahoo/config/model/ConfigModelRegistry.java
@@ -5,7 +5,7 @@ import com.yahoo.config.model.builder.xml.ConfigModelBuilder;
 import com.yahoo.config.model.builder.xml.ConfigModelId;
 
 import java.util.Collection;
-import java.util.Collections;
+import java.util.List;
 
 /**
  * A resolver of implementations of named config models.
@@ -44,7 +44,7 @@ public abstract class ConfigModelRegistry {
 
         @Override
         public Collection<ConfigModelBuilder> resolve(ConfigModelId id) {
-            return Collections.emptyList();
+            return List.of();
         }
     }
 
diff --git a/config-model/src/main/java/com/yahoo/config/model/deploy/DeployState.java b/config-model/src/main/java/com/yahoo/config/model/deploy/DeployState.java
index f19341098f4..57a75bd8a38 100644
--- a/config-model/src/main/java/com/yahoo/config/model/deploy/DeployState.java
+++ b/config-model/src/main/java/com/yahoo/config/model/deploy/DeployState.java
@@ -50,7 +50,6 @@ import java.io.Reader;
 import java.io.UncheckedIOException;
 import java.time.Instant;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -329,7 +328,7 @@ public class DeployState implements ConfigDefinitionStore {
         private Optional<ConfigDefinitionRepo> configDefinitionRepo = Optional.empty();
         private Optional<Model> previousModel = Optional.empty();
         private Set<ContainerEndpoint> endpoints = Set.of();
-        private Collection<MlModelImporter> modelImporters = Collections.emptyList();
+        private Collection<MlModelImporter> modelImporters = List.of();
         private Zone zone = Zone.defaultZone();
         private Instant now = Instant.now();
         private Version wantedNodeVespaVersion = Vtag.currentVersion;
diff --git a/config-model/src/main/java/com/yahoo/config/model/deploy/TestProperties.java b/config-model/src/main/java/com/yahoo/config/model/deploy/TestProperties.java
index 11d3a48ee51..3e91b8afe88 100644
--- a/config-model/src/main/java/com/yahoo/config/model/deploy/TestProperties.java
+++ b/config-model/src/main/java/com/yahoo/config/model/deploy/TestProperties.java
@@ -19,7 +19,6 @@ import com.yahoo.vespa.model.container.ApplicationContainerCluster;
 import java.net.URI;
 import java.security.cert.X509Certificate;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
@@ -35,10 +34,10 @@ public class TestProperties implements ModelContext.Properties, ModelContext.Fea
 
     private boolean multitenant = false;
     private ApplicationId applicationId = ApplicationId.defaultId();
-    private List<ConfigServerSpec> configServerSpecs = Collections.emptyList();
+    private List<ConfigServerSpec> configServerSpecs = List.of();
     private boolean hostedVespa = false;
     private Zone zone = Zone.defaultZone();
-    private final Set<ContainerEndpoint> endpoints = Collections.emptySet();
+    private final Set<ContainerEndpoint> endpoints = Set.of();
     private boolean useDedicatedNodeForLogserver = false;
     private double defaultTermwiseLimit = 1.0;
     private String jvmGCOptions = null;
@@ -55,10 +54,10 @@ public class TestProperties implements ModelContext.Properties, ModelContext.Fea
     private double feedConcurrency = 0.5;
     private double feedNiceness = 0.0;
     private int maxActivationInhibitedOutOfSyncGroups = 0;
-    private List<TenantSecretStore> tenantSecretStores = Collections.emptyList();
+    private List<TenantSecretStore> tenantSecretStores = List.of();
     private String jvmOmitStackTraceInFastThrowOption;
     private boolean allowDisableMtls = true;
-    private List<X509Certificate> operatorCertificates = Collections.emptyList();
+    private List<X509Certificate> operatorCertificates = List.of();
     private double resourceLimitDisk = 0.75;
     private double resourceLimitMemory = 0.8;
     private double minNodeRatioPerGroup = 0.0;
diff --git a/config-model/src/main/java/com/yahoo/config/model/graph/ModelNode.java b/config-model/src/main/java/com/yahoo/config/model/graph/ModelNode.java
index e411a8e3e77..dcf1c8629a4 100644
--- a/config-model/src/main/java/com/yahoo/config/model/graph/ModelNode.java
+++ b/config-model/src/main/java/com/yahoo/config/model/graph/ModelNode.java
@@ -135,7 +135,7 @@ public class ModelNode<MODEL extends ConfigModel> implements ConfigModelInstance
         }
         // For collections, we don't require that dependency has been added, we just give an empty collection
         if (isCollection(param))
-            return Collections.emptyList();
+            return List.of();
         throw new IllegalArgumentException("Unable to find constructor argument " + param + " for " + clazz.getName());
     }
 
diff --git a/config-model/src/main/java/com/yahoo/config/model/test/MockApplicationPackage.java b/config-model/src/main/java/com/yahoo/config/model/test/MockApplicationPackage.java
index 5d3db7f676a..365543a549b 100644
--- a/config-model/src/main/java/com/yahoo/config/model/test/MockApplicationPackage.java
+++ b/config-model/src/main/java/com/yahoo/config/model/test/MockApplicationPackage.java
@@ -31,7 +31,6 @@ import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -143,7 +142,7 @@ public class MockApplicationPackage implements ApplicationPackage {
 
     @Override
     public Map<ConfigDefinitionKey, UnparsedConfigDefinition> getAllExistingConfigDefs() {
-        return Collections.emptyMap();
+        return Map.of();
     }
 
     @Override
@@ -203,7 +202,7 @@ public class MockApplicationPackage implements ApplicationPackage {
     }
 
     public List<ComponentInfo> getComponentsInfo(Version vespaVersion) {
-        return Collections.emptyList();
+        return List.of();
     }
 
     public QueryProfileRegistry getQueryProfiles() { return queryProfileRegistry; }
@@ -240,7 +239,7 @@ public class MockApplicationPackage implements ApplicationPackage {
         private File root = new File("nonexisting");
         private String hosts = null;
         private String services = null;
-        private List<String> schemas = Collections.emptyList();
+        private List<String> schemas = List.of();
         private Map<Path, MockApplicationFile> files = new LinkedHashMap<>();
         private String schemaDir = null;
         private String deploymentSpec = null;
@@ -277,12 +276,12 @@ public class MockApplicationPackage implements ApplicationPackage {
         }
 
         public Builder withSearchDefinition(String searchDefinition) {
-            this.schemas = Collections.singletonList(searchDefinition);
+            this.schemas = List.of(searchDefinition);
             return this;
         }
 
         public Builder withSchemas(List<String> searchDefinition) {
-            this.schemas = Collections.unmodifiableList(searchDefinition);
+            this.schemas = List.copyOf(searchDefinition);
             return this;
         }
 
@@ -369,8 +368,8 @@ public class MockApplicationPackage implements ApplicationPackage {
     }
 
     private List<NamedReader> asNamedReaderList(String value) {
-        if (value == null) return Collections.emptyList();
-        return Collections.singletonList(new NamedReader(extractId(value) + ".xml", new StringReader(value)));
+        if (value == null) return List.of();
+        return List.of(new NamedReader(extractId(value) + ".xml", new StringReader(value)));
     }
 
     private String extractId(String xmlStringWithIdAttribute) {
diff --git a/config-model/src/main/java/com/yahoo/documentmodel/NewDocumentType.java b/config-model/src/main/java/com/yahoo/documentmodel/NewDocumentType.java
index 77e123fefef..c5140dd6fc8 100644
--- a/config-model/src/main/java/com/yahoo/documentmodel/NewDocumentType.java
+++ b/config-model/src/main/java/com/yahoo/documentmodel/NewDocumentType.java
@@ -25,7 +25,6 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 
-import static java.util.Collections.emptySet;
 
 /**
  * @author baldersheim
@@ -47,7 +46,7 @@ public final class NewDocumentType extends StructuredDataType implements DataTyp
     private final Set<String> importedFieldNames;
 
     public NewDocumentType(Name name) {
-        this(name, emptySet());
+        this(name, Set.of());
     }
 
     public NewDocumentType(Name name, Set<Name> documentReferences, Set<String> importedFieldNames) {
@@ -60,7 +59,7 @@ public final class NewDocumentType extends StructuredDataType implements DataTyp
     }
 
     public NewDocumentType(Name name, Set<Name> documentReferences) {
-        this(name, documentReferences, emptySet());
+        this(name, documentReferences, Set.of());
     }
 
     public NewDocumentType(Name name,
@@ -74,8 +73,8 @@ public final class NewDocumentType extends StructuredDataType implements DataTyp
         if (fs != null) {
             this.fieldSets.addAll(fs.userFieldSets().values());
             for (FieldSet f : fs.builtInFieldSets().values()) {
-                if ((f.getName() != BuiltInFieldSets.INTERNAL_FIELDSET_NAME) &&
-                    (f.getName() != BuiltInFieldSets.SEARCH_FIELDSET_NAME)) {
+                if (!BuiltInFieldSets.INTERNAL_FIELDSET_NAME.equals(f.getName()) &&
+                    !BuiltInFieldSets.SEARCH_FIELDSET_NAME.equals(f.getName())) {
                     fieldSets.add(f);
                 }
             }
diff --git a/config-model/src/main/java/com/yahoo/schema/ApplicationBuilder.java b/config-model/src/main/java/com/yahoo/schema/ApplicationBuilder.java
index 2e964ac3624..749cdbfd8b7 100644
--- a/config-model/src/main/java/com/yahoo/schema/ApplicationBuilder.java
+++ b/config-model/src/main/java/com/yahoo/schema/ApplicationBuilder.java
@@ -27,7 +27,6 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
@@ -351,7 +350,7 @@ public class ApplicationBuilder {
                                                      RankProfileRegistry rankProfileRegistry,
                                                      QueryProfileRegistry queryprofileRegistry)
             throws IOException, ParseException {
-        return createFromFiles(Collections.singletonList(fileName), new MockFileRegistry(), deployLogger, new TestProperties(),
+        return createFromFiles(List.of(fileName), new MockFileRegistry(), deployLogger, new TestProperties(),
                                rankProfileRegistry, queryprofileRegistry);
     }
 
@@ -414,8 +413,8 @@ public class ApplicationBuilder {
                                                             queryProfileRegistry);
 
         var fnli = Files.list(new File(dir).toPath())
-            .map(p -> p.toString())
-            .filter(fn -> AbstractApplicationPackage.validSchemaFilename(fn))
+            .map(java.nio.file.Path::toString)
+            .filter(AbstractApplicationPackage::validSchemaFilename)
             .sorted();
         for (var i = fnli.iterator(); i.hasNext(); ) {
             builder.addSchemaFile(i.next());
diff --git a/config-model/src/main/java/com/yahoo/schema/FieldSets.java b/config-model/src/main/java/com/yahoo/schema/FieldSets.java
index 1dbf496992b..6464bd1681e 100644
--- a/config-model/src/main/java/com/yahoo/schema/FieldSets.java
+++ b/config-model/src/main/java/com/yahoo/schema/FieldSets.java
@@ -47,11 +47,7 @@ public class FieldSets {
      * @param field field to add to field set
      */
     public void addBuiltInFieldSetItem(String setName, String field) {
-        if (builtInFieldSets.get(setName) == null) {
-            // First entry in this set
-            builtInFieldSets.put(setName, new FieldSet(setName));
-        }
-        builtInFieldSets.get(setName).addFieldName(field);
+        builtInFieldSets.computeIfAbsent(setName, FieldSet::new).addFieldName(field);
     }
 
     /** Returns the built in field sets, unmodifiable */
diff --git a/config-model/src/main/java/com/yahoo/schema/RankProfile.java b/config-model/src/main/java/com/yahoo/schema/RankProfile.java
index 22bf1880cd7..82ed45028b3 100644
--- a/config-model/src/main/java/com/yahoo/schema/RankProfile.java
+++ b/config-model/src/main/java/com/yahoo/schema/RankProfile.java
@@ -32,7 +32,6 @@ import java.io.IOException;
 import java.io.Reader;
 import java.io.StringReader;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -487,12 +486,12 @@ public class RankProfile implements Cloneable {
     }
 
     void setFirstPhaseRanking(RankingExpression rankingExpression) {
-        this.firstPhaseRanking = new RankingExpressionFunction(new ExpressionFunction(FIRST_PHASE, Collections.emptyList(), rankingExpression), false);
+        this.firstPhaseRanking = new RankingExpressionFunction(new ExpressionFunction(FIRST_PHASE, List.of(), rankingExpression), false);
     }
 
     public void setFirstPhaseRanking(String expression) {
         try {
-            firstPhaseRanking = new RankingExpressionFunction(parseRankingExpression(FIRST_PHASE, Collections.emptyList(), expression), false);
+            firstPhaseRanking = new RankingExpressionFunction(parseRankingExpression(FIRST_PHASE, List.of(), expression), false);
         } catch (ParseException e) {
             throw new IllegalArgumentException("Illegal first phase ranking function", e);
         }
@@ -515,7 +514,7 @@ public class RankProfile implements Cloneable {
 
     public void setSecondPhaseRanking(String expression) {
         try {
-            secondPhaseRanking = new RankingExpressionFunction(parseRankingExpression(SECOND_PHASE, Collections.emptyList(), expression), false);
+            secondPhaseRanking = new RankingExpressionFunction(parseRankingExpression(SECOND_PHASE, List.of(), expression), false);
         }
         catch (ParseException e) {
             throw new IllegalArgumentException("Illegal second phase ranking function", e);
@@ -535,7 +534,7 @@ public class RankProfile implements Cloneable {
 
     public void setGlobalPhaseRanking(String expression) {
         try {
-            globalPhaseRanking = new RankingExpressionFunction(parseRankingExpression(GLOBAL_PHASE, Collections.emptyList(), expression), false);
+            globalPhaseRanking = new RankingExpressionFunction(parseRankingExpression(GLOBAL_PHASE, List.of(), expression), false);
         }
         catch (ParseException e) {
             throw new IllegalArgumentException("Illegal global-phase ranking function", e);
@@ -1036,7 +1035,7 @@ public class RankProfile implements Cloneable {
         Map<Reference, TensorType> featureTypes = featureTypes();
         // Function compiling first pass: compile inline functions without resolving other functions
         Map<String, RankingExpressionFunction> inlineFunctions =
-                compileFunctions(this::getInlineFunctions, queryProfiles, featureTypes, importedModels, Collections.emptyMap(), expressionTransforms);
+                compileFunctions(this::getInlineFunctions, queryProfiles, featureTypes, importedModels, Map.of(), expressionTransforms);
 
         firstPhaseRanking = compile(this.getFirstPhase(), queryProfiles, featureTypes, importedModels, constants(), inlineFunctions, expressionTransforms);
         secondPhaseRanking = compile(this.getSecondPhase(), queryProfiles, featureTypes, importedModels, constants(), inlineFunctions, expressionTransforms);
diff --git a/config-model/src/main/java/com/yahoo/schema/derived/Deriver.java b/config-model/src/main/java/com/yahoo/schema/derived/Deriver.java
index 9774868db9c..0c669e29538 100644
--- a/config-model/src/main/java/com/yahoo/schema/derived/Deriver.java
+++ b/config-model/src/main/java/com/yahoo/schema/derived/Deriver.java
@@ -7,7 +7,6 @@ import com.yahoo.schema.parser.ParseException;
 import com.yahoo.vespa.configmodel.producers.DocumentManager;
 import com.yahoo.vespa.configmodel.producers.DocumentTypes;
 import java.io.IOException;
-import java.util.Collections;
 import java.util.List;
 
 /**
@@ -30,7 +29,7 @@ public class Deriver {
     }
 
     public static DocumentmanagerConfig.Builder getDocumentManagerConfig(String sd) {
-        return getDocumentManagerConfig(Collections.singletonList(sd));
+        return getDocumentManagerConfig(List.of(sd));
     }
 
     public static DocumentmanagerConfig.Builder getDocumentManagerConfig(List<String> schemas) {
@@ -38,7 +37,7 @@ public class Deriver {
     }
 
     public static DocumenttypesConfig.Builder getDocumentTypesConfig(String schema) {
-        return getDocumentTypesConfig(Collections.singletonList(schema));
+        return getDocumentTypesConfig(List.of(schema));
     }
 
     public static DocumenttypesConfig.Builder getDocumentTypesConfig(List<String> schemas) {
diff --git a/config-model/src/main/java/com/yahoo/schema/derived/IndexSchema.java b/config-model/src/main/java/com/yahoo/schema/derived/IndexSchema.java
index 34ed9f2f60c..677e4b31bdf 100644
--- a/config-model/src/main/java/com/yahoo/schema/derived/IndexSchema.java
+++ b/config-model/src/main/java/com/yahoo/schema/derived/IndexSchema.java
@@ -14,7 +14,6 @@ import com.yahoo.vespa.config.search.IndexschemaConfig;
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
@@ -147,7 +146,7 @@ public class IndexSchema extends Derived {
     static List<Field> flattenField(Field field) {
         DataType fieldType = field.getDataType();
         if (fieldType.getPrimitiveType() != null){
-            return Collections.singletonList(field);
+            return List.of(field);
         }
         if (fieldType instanceof ArrayDataType) {
             List<Field> ret = new LinkedList<>();
diff --git a/config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedSDField.java b/config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedSDField.java
index cb98cb79e01..7ade7ada061 100644
--- a/config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedSDField.java
+++ b/config-model/src/main/java/com/yahoo/schema/document/ImmutableImportedSDField.java
@@ -10,7 +10,6 @@ import com.yahoo.vespa.indexinglanguage.expressions.Expression;
 import com.yahoo.vespa.indexinglanguage.expressions.ScriptExpression;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -131,7 +130,7 @@ public class ImmutableImportedSDField implements ImmutableSDField {
 
     @Override
     public Map<String, String> getAliasToName() {
-        return Collections.emptyMap();
+        return Map.of();
     }
 
     @Override
diff --git a/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java b/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java
index be129b53c5e..b5d1cf71809 100644
--- a/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java
+++ b/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java
@@ -106,7 +106,7 @@ public class IndexingOutputs extends Processor {
         MyConverter(Schema schema, Field field, Set<String> summaryFields, boolean validate) {
             this.schema = schema;
             this.field = field;
-            this.summaryFields = summaryFields.isEmpty() ? Collections.singleton(field.getName()) : summaryFields;
+            this.summaryFields = summaryFields.isEmpty() ? Set.of(field.getName()) : summaryFields;
             this.validate = validate;
         }
 
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/HostPorts.java b/config-model/src/main/java/com/yahoo/vespa/model/HostPorts.java
index f1d3b38e8ff..348a5d575eb 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/HostPorts.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/HostPorts.java
@@ -4,7 +4,6 @@ package com.yahoo.vespa.model;
 
 import com.yahoo.config.application.api.DeployLogger;
 import com.yahoo.config.provision.NetworkPorts;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -28,7 +27,7 @@ public class HostPorts {
 
     private int allocatedPorts = 0;
 
-    private PortFinder portFinder = new PortFinder(Collections.emptyList());
+    private PortFinder portFinder = new PortFinder(List.of());
 
     private boolean flushed = false;
     private Optional<NetworkPorts> networkPortsList = Optional.empty();
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java b/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java
index 1c4b0d31ab2..c876976917b 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java
@@ -36,7 +36,6 @@ import java.io.IOException;
 import java.time.Clock;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.logging.Level;
@@ -96,7 +95,7 @@ public class VespaModelFactory implements ModelFactory {
         } else {
             this.configModelRegistry = configModelRegistry;
         }
-        this.modelImporters = Collections.emptyList();
+        this.modelImporters = List.of();
         this.additionalValidators = List.of();
         this.zone = zone;
         this.clock = clock;
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/admin/clustercontroller/ClusterControllerContainerCluster.java b/config-model/src/main/java/com/yahoo/vespa/model/admin/clustercontroller/ClusterControllerContainerCluster.java
index 78ef6826d26..c19d186df42 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/admin/clustercontroller/ClusterControllerContainerCluster.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/admin/clustercontroller/ClusterControllerContainerCluster.java
@@ -10,7 +10,6 @@ import com.yahoo.vespa.model.container.ContainerCluster;
 import com.yahoo.vespa.model.container.PlatformBundles;
 
 import java.nio.file.Path;
-import java.util.Collections;
 import java.util.Optional;
 import java.util.Set;
 
@@ -22,7 +21,7 @@ import java.util.Set;
  */
 public class ClusterControllerContainerCluster extends ContainerCluster<ClusterControllerContainer> {
 
-    private static final Set<Path> UNNECESSARY_BUNDLES = Collections.unmodifiableSet(PlatformBundles.VESPA_SECURITY_BUNDLES);
+    private static final Set<Path> UNNECESSARY_BUNDLES = Set.copyOf(PlatformBundles.VESPA_SECURITY_BUNDLES);
 
     private final ReindexingContext reindexingContext;
 
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsProxyContainerCluster.java b/config-model/src/main/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsProxyContainerCluster.java
index 0d85696d503..913ae0e1a00 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsProxyContainerCluster.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsProxyContainerCluster.java
@@ -36,7 +36,6 @@ import com.yahoo.vespa.model.container.component.Handler;
 import com.yahoo.vespa.model.container.component.SystemBindingPattern;
 
 import java.nio.file.Path;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Optional;
@@ -198,7 +197,7 @@ public class MetricsProxyContainerCluster extends ContainerCluster<MetricsProxyC
     private Map<String, MetricsConsumer> getUserMetricsConsumers() {
         return getAdmin()
                 .map(admin -> admin.getUserMetrics().getConsumers())
-                .orElse(Collections.emptyMap());
+                .orElse(Map.of());
     }
 
     private Optional<String> getSystemName() {
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/ComponentsBuilder.java b/config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/ComponentsBuilder.java
index 046980087ed..bde12bb1d5a 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/ComponentsBuilder.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/ComponentsBuilder.java
@@ -151,7 +151,7 @@ public class ComponentsBuilder<T extends ChainedComponent<?>> {
     private Map<String, ComponentType<?>> unmodifiable(Map<String, ComponentType<?>> outerComponentTypeByComponentName) {
         return (outerComponentTypeByComponentName != null)?
                 Collections.unmodifiableMap(outerComponentTypeByComponentName):
-                Collections.emptyMap();
+                Map.of();
     }
 
     public Collection<T> getComponentDefinitions() {
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/container/PlatformBundles.java b/config-model/src/main/java/com/yahoo/vespa/model/container/PlatformBundles.java
index baa9c4b9a48..9f91f6bf5e1 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/container/PlatformBundles.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/container/PlatformBundles.java
@@ -69,7 +69,7 @@ public class PlatformBundles {
     private static Set<Path> toBundlePaths(String... bundleNames) {
         return Stream.of(bundleNames)
                 .map(PlatformBundles::absoluteBundlePath)
-                .collect(Collectors.toSet());
+                .collect(Collectors.toUnmodifiableSet());
     }
 
     public static Path absoluteBundlePath(String fileName) {
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/container/component/DiscBindingsConfigGenerator.java b/config-model/src/main/java/com/yahoo/vespa/model/container/component/DiscBindingsConfigGenerator.java
index ed626f98aa0..dafac2c1af9 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/container/component/DiscBindingsConfigGenerator.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/container/component/DiscBindingsConfigGenerator.java
@@ -2,7 +2,6 @@
 package com.yahoo.vespa.model.container.component;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
@@ -24,9 +23,9 @@ public class DiscBindingsConfigGenerator {
 
     public static <T extends Handler> Map<String, Handlers.Builder> generate(T handler) {
         if (handler.getServerBindings().isEmpty() && handler.getClientBindings().isEmpty())
-            return Collections.emptyMap();
+            return Map.of();
 
-        return Collections.singletonMap(handler.model.getComponentId().stringValue(),
+        return Map.of(handler.model.getComponentId().stringValue(),
                             new Handlers.Builder()
                                     .serverBindings(toStrings(handler.getServerBindings()))
                                     .clientBindings(toStrings(handler.getClientBindings())));
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/container/http/AccessControl.java b/config-model/src/main/java/com/yahoo/vespa/model/container/http/AccessControl.java
index 8c1b868465a..19c45bba2ef 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/container/http/AccessControl.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/container/http/AccessControl.java
@@ -48,7 +48,7 @@ public class AccessControl {
         private final String domain;
         private ClientAuthentication clientAuthentication = ClientAuthentication.need;
         private final Set<BindingPattern> excludeBindings = new LinkedHashSet<>();
-        private Collection<Handler> handlers = Collections.emptyList();
+        private Collection<Handler> handlers = List.of();
         public Builder(String domain) {
             this.domain = domain;
         }
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainBuilder.java b/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainBuilder.java
index bc234546625..82a8a01871e 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainBuilder.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainBuilder.java
@@ -11,7 +11,7 @@ import com.yahoo.vespa.model.container.http.HttpFilterChain;
 import org.w3c.dom.Element;
 
 import java.util.Collection;
-import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 
 import static com.yahoo.vespa.model.builder.xml.dom.chains.ComponentsBuilder.ComponentType;
@@ -21,7 +21,7 @@ import static com.yahoo.vespa.model.builder.xml.dom.chains.ComponentsBuilder.Com
  */
 public class FilterChainBuilder extends DomChainBuilderBase<Filter, HttpFilterChain> {
 
-    private static final Collection<ComponentType<Filter>> allowedComponentTypes = Collections.singleton(ComponentType.filter);
+    private static final Collection<ComponentType<Filter>> allowedComponentTypes = List.of(ComponentType.filter);
 
     public FilterChainBuilder(Map<String, ComponentType<?>> outerFilterTypeByComponentName) {
         super(allowedComponentTypes, outerFilterTypeByComponentName);
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainsBuilder.java b/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainsBuilder.java
index 878859a01bf..f1cdbfb3b04 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainsBuilder.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/container/http/xml/FilterChainsBuilder.java
@@ -15,7 +15,6 @@ import com.yahoo.vespa.model.container.http.HttpFilterChain;
 import org.w3c.dom.Element;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -24,7 +23,7 @@ import java.util.Map;
  */
 public class FilterChainsBuilder extends DomChainsBuilder<Filter, HttpFilterChain, FilterChains>  {
     private static final Collection<ComponentType<Filter>> allowedComponentTypes =
-            Collections.singleton(ComponentType.filter);
+            List.of(ComponentType.filter);
 
     private static final Map<String, Class<? extends DomChainBuilderBase<? extends Filter, ? extends HttpFilterChain>>> chainType2BuilderClass =
             Map.of(
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java b/config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java
index 456ce8fdbc2..360a02256a9 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java
@@ -114,7 +114,6 @@ import java.security.cert.X509Certificate;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -893,7 +892,7 @@ public class ContainerModelBuilder extends ConfigModelBuilder<ContainerModel> {
 
     private void addStandaloneNode(ApplicationContainerCluster cluster, DeployState deployState) {
         ApplicationContainer container = new ApplicationContainer(cluster, "standalone", cluster.getContainers().size(), deployState);
-        cluster.addContainers(Collections.singleton(container));
+        cluster.addContainers(List.of(container));
     }
 
     private static String buildJvmGCOptions(ConfigModelContext context, String jvmGCOptions) {
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/content/Content.java b/config-model/src/main/java/com/yahoo/vespa/model/content/Content.java
index 9d15eddbef3..6d482a6d4a6 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/content/Content.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/content/Content.java
@@ -35,7 +35,6 @@ import org.w3c.dom.Element;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Optional;
@@ -195,7 +194,7 @@ public class Content extends ConfigModel {
 
     public static class Builder extends ConfigModelBuilder<Content> {
     
-        public static final List<ConfigModelId> configModelIds = Collections.singletonList(ConfigModelId.fromName("content"));
+        public static final List<ConfigModelId> configModelIds = List.of(ConfigModelId.fromName("content"));
     
         public Builder() {
             super(Content.class);
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/content/StorageGroup.java b/config-model/src/main/java/com/yahoo/vespa/model/content/StorageGroup.java
index a6f53777c51..a1b9ed67aa7 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/content/StorageGroup.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/content/StorageGroup.java
@@ -19,7 +19,6 @@ import com.yahoo.vespa.model.content.engines.PersistenceEngine;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -349,7 +348,7 @@ public class StorageGroup {
                                        owner.getStorageCluster().getClusterName(),
                                        owner.getRoot().hostSystem(),
                                        context) :
-                        Collections.emptyMap();
+                        Map.of();
 
                 Map<Optional<ClusterSpec.Group>, Map<HostResource, ClusterMembership>> hostGroups = collectAllocatedSubgroups(hostMapping);
                 if (hostGroups.size() > 1) {
@@ -475,7 +474,7 @@ public class StorageGroup {
         }
 
         private List<XmlNodeBuilder> collectExplicitNodes(Optional<ModelElement> groupOrNodesElement) {
-            if (groupOrNodesElement.isEmpty()) return Collections.emptyList();
+            if (groupOrNodesElement.isEmpty()) return List.of();
             List<XmlNodeBuilder> nodes = new ArrayList<>();
             for (ModelElement n : groupOrNodesElement.get().subElements("node"))
                 nodes.add(new XmlNodeBuilder(clusterElement, n));
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/content/cluster/GlobalDistributionBuilder.java b/config-model/src/main/java/com/yahoo/vespa/model/content/cluster/GlobalDistributionBuilder.java
index c9b6537434b..07dafda164d 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/content/cluster/GlobalDistributionBuilder.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/content/cluster/GlobalDistributionBuilder.java
@@ -4,7 +4,6 @@ package com.yahoo.vespa.model.content.cluster;
 import com.yahoo.documentmodel.NewDocumentType;
 import com.yahoo.vespa.model.builder.xml.dom.ModelElement;
 
-import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
@@ -20,19 +19,19 @@ public class GlobalDistributionBuilder {
     private final Map<String, NewDocumentType> documentDefinitions;
 
     public GlobalDistributionBuilder(Map<String, NewDocumentType> documentDefinitions) {
-        this.documentDefinitions = Collections.unmodifiableMap(documentDefinitions);
+        this.documentDefinitions = Map.copyOf(documentDefinitions);
     }
 
     public Set<NewDocumentType> build(ModelElement documentsElement) {
         if (documentsElement == null || documentsElement.subElements("document").isEmpty())
-            return Collections.emptySet();
+            return Set.of();
 
         return documentsElement.subElements("document")
                 .stream()
                 .filter(GlobalDistributionBuilder::isGloballyDistributed)
                 .map(GlobalDistributionBuilder::getDocumentName)
                 .map(this::getDocumentType)
-                .collect(Collectors.toCollection(() -> new LinkedHashSet<>()));
+                .collect(Collectors.toCollection(LinkedHashSet::new));
     }
 
     private static boolean isGloballyDistributed(ModelElement e) {
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/ml/ConvertedModel.java b/config-model/src/main/java/com/yahoo/vespa/model/ml/ConvertedModel.java
index 621377e0606..78ed10a583e 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/ml/ConvertedModel.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/ml/ConvertedModel.java
@@ -32,7 +32,6 @@ import java.io.StringReader;
 import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -177,7 +176,7 @@ public class ConvertedModel {
         if (arguments.output().isEmpty()) {
             List<Map.Entry<String, ExpressionFunction>> entriesWithTheRightPrefix =
                     expressions.entrySet().stream().filter(entry -> entry.getKey().startsWith(arguments.signature().get() + ".")).toList();
-            if (entriesWithTheRightPrefix.size() < 1)
+            if (entriesWithTheRightPrefix.isEmpty())
                 throw new IllegalArgumentException("No expressions named '" + arguments.signature().get() +
                                                    missingExpressionMessageSuffix());
             if (entriesWithTheRightPrefix.size() > 1)
@@ -191,7 +190,7 @@ public class ConvertedModel {
 
     private String missingExpressionMessageSuffix() {
         return "' in model '" + modelDescription + "'. " +
-               "Available expressions: " + expressions.keySet().stream().collect(Collectors.joining(", "));
+               "Available expressions: " + String.join(", ", expressions.keySet());
     }
 
     // ----------------------- Static model conversion/storage below here
@@ -425,8 +424,7 @@ public class ConvertedModel {
     }
 
     private static void addFunctionNamesIn(ExpressionNode node, Set<String> names, ImportedMlModel model) {
-        if (node instanceof ReferenceNode) {
-            ReferenceNode referenceNode = (ReferenceNode)node;
+        if (node instanceof ReferenceNode referenceNode) {
             if (referenceNode.getOutput() == null) { // function references cannot specify outputs
                 if (names.add(referenceNode.getName())) {
                     if (model.functions().containsKey(referenceNode.getName())) {
@@ -485,7 +483,7 @@ public class ConvertedModel {
         List<Pair<String, ExpressionFunction>> readExpressions() {
             List<Pair<String, ExpressionFunction>> expressions = new ArrayList<>();
             ApplicationFile expressionPath = application.getFile(modelFiles.expressionsPath());
-            if ( ! expressionPath.exists() || ! expressionPath.isDirectory()) return Collections.emptyList();
+            if ( ! expressionPath.exists() || ! expressionPath.isDirectory()) return List.of();
             for (ApplicationFile expressionFile : expressionPath.listFiles()) {
                 try (BufferedReader reader = new BufferedReader(expressionFile.createReader())) {
                     String name = expressionFile.getPath().getName();
@@ -525,7 +523,7 @@ public class ConvertedModel {
         List<Pair<String, RankingExpression>> readFunctions() {
             try {
                 ApplicationFile file = application.getFile(modelFiles.functionsPath());
-                if ( ! file.exists()) return Collections.emptyList();
+                if ( ! file.exists()) return List.of();
 
                 List<Pair<String, RankingExpression>> functions = new ArrayList<>();
                 try (BufferedReader reader = new BufferedReader(file.createReader())) {
@@ -597,7 +595,7 @@ public class ConvertedModel {
         private List<Pair<String, Tensor>> readSmallConstants() {
             try {
                 ApplicationFile file = application.getFile(modelFiles.smallConstantsPath());
-                if ( ! file.exists()) return Collections.emptyList();
+                if ( ! file.exists()) return List.of();
 
                 List<Pair<String, Tensor>> constants = new ArrayList<>();
                 BufferedReader reader = new BufferedReader(file.createReader());
diff --git a/config-model/src/main/java/com/yahoo/vespa/model/ml/OnnxModelInfo.java b/config-model/src/main/java/com/yahoo/vespa/model/ml/OnnxModelInfo.java
index 502924ed31a..f47a48b09d7 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/ml/OnnxModelInfo.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/ml/OnnxModelInfo.java
@@ -17,7 +17,6 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -51,8 +50,8 @@ public class OnnxModelInfo {
                           Map<String, OnnxTypeInfo> outputs, Set<String> initializers, String defaultOutput) {
         this.app = app;
         this.modelPath = path;
-        this.inputs = Collections.unmodifiableMap(inputs);
-        this.outputs = Collections.unmodifiableMap(outputs);
+        this.inputs = Map.copyOf(inputs);
+        this.outputs = Map.copyOf(outputs);
         this.defaultOutput = defaultOutput;
         this.initializers = Set.copyOf(initializers);
     }
diff --git a/config-model/src/test/java/com/yahoo/config/model/MapConfigModelRegistryTest.java b/config-model/src/test/java/com/yahoo/config/model/MapConfigModelRegistryTest.java
index cb232c4f812..900799b86a1 100644
--- a/config-model/src/test/java/com/yahoo/config/model/MapConfigModelRegistryTest.java
+++ b/config-model/src/test/java/com/yahoo/config/model/MapConfigModelRegistryTest.java
@@ -7,7 +7,6 @@ import org.junit.jupiter.api.Test;
 import org.w3c.dom.Element;
 
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 
 import static org.junit.jupiter.api.Assertions.*;
@@ -47,7 +46,7 @@ public class MapConfigModelRegistryTest {
         }
 
         @Override
-        public List<ConfigModelId> handlesElements() { return Collections.singletonList(ConfigModelId.fromName("modelB")); }
+        public List<ConfigModelId> handlesElements() { return List.of(ConfigModelId.fromName("modelB")); }
         @Override
         public void doBuild(ModelB model, Element spec, ConfigModelContext modelContext) { }
     }
@@ -57,7 +56,7 @@ public class MapConfigModelRegistryTest {
             super(ModelB.class);
         }
         @Override
-        public List<ConfigModelId> handlesElements() { return Collections.singletonList(ConfigModelId.fromName("modelB")); }
+        public List<ConfigModelId> handlesElements() { return List.of(ConfigModelId.fromName("modelB")); }
         @Override
         public void doBuild(ModelB model, Element spec, ConfigModelContext modelContext) { }
     }
@@ -73,7 +72,7 @@ public class MapConfigModelRegistryTest {
             super(ModelA.class);
         }
         @Override
-        public List<ConfigModelId> handlesElements() { return Collections.singletonList(ConfigModelId.fromName("modelA")); }
+        public List<ConfigModelId> handlesElements() { return List.of(ConfigModelId.fromName("modelA")); }
 
         @Override
         public void doBuild(ModelA model, Element spec, ConfigModelContext modelContext) { }
diff --git a/config-model/src/test/java/com/yahoo/config/model/provision/HostsXmlProvisionerTest.java b/config-model/src/test/java/com/yahoo/config/model/provision/HostsXmlProvisionerTest.java
index 51574432e6d..02ca9effffb 100644
--- a/config-model/src/test/java/com/yahoo/config/model/provision/HostsXmlProvisionerTest.java
+++ b/config-model/src/test/java/com/yahoo/config/model/provision/HostsXmlProvisionerTest.java
@@ -8,7 +8,6 @@ import org.junit.jupiter.api.Test;
 import java.io.StringReader;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -22,27 +21,29 @@ import static org.junit.jupiter.api.Assertions.*;
  */
 public class HostsXmlProvisionerTest {
 
-    private static final String oneHost = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" +
-            "<hosts>\n" +
-            "    <host name=\"test1.yahoo.com\">\n" +
-            "        <alias>node1</alias>\n" +
-            "        <alias>node2</alias>\n" +
-            "    </host>\n" +
-            "</hosts>";
-
-    private static final String threeHosts = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n" +
-            "<hosts>\n" +
-            "    <host name=\"test1.yahoo.com\">\n" +
-            "        <alias>node1</alias>\n" +
-            "    </host>\n" +
-            "    <host name=\"test2.yahoo.com\">\n" +
-            "        <alias>node2</alias>\n" +
-            "        <alias>node3</alias>\n" +
-            "    </host>\n" +
-            "    <host name=\"test3.yahoo.com\">\n" +
-            "        <alias>node4</alias>\n" +
-            "    </host>\n" +
-            "</hosts>";
+    private static final String oneHost = """
+            <?xml version="1.0" encoding="utf-8"?>
+            <hosts>
+                <host name="test1.yahoo.com">
+                    <alias>node1</alias>
+                    <alias>node2</alias>
+                </host>
+            </hosts>""";
+
+    private static final String threeHosts = """
+            <?xml version="1.0" encoding="utf-8"?>
+            <hosts>
+                <host name="test1.yahoo.com">
+                    <alias>node1</alias>
+                </host>
+                <host name="test2.yahoo.com">
+                    <alias>node2</alias>
+                    <alias>node3</alias>
+                </host>
+                <host name="test3.yahoo.com">
+                    <alias>node4</alias>
+                </host>
+            </hosts>""";
 
     @Test
     void require_basic_works() {
@@ -57,7 +58,7 @@ public class HostsXmlProvisionerTest {
         assertTrue(map.keySet().containsAll(aliases));
 
         // 5 services, 3 host aliases, mapping to 2 host.
-        aliases = createAliases(Collections.singletonList("node3"));
+        aliases = createAliases(List.of("node3"));
         map = allocate(hostProvisioner, aliases);
 
         assertCorrectNumberOfHosts(map, 2);
@@ -65,7 +66,7 @@ public class HostsXmlProvisionerTest {
         assertTrue(map.keySet().containsAll(aliases));
 
         // 5 services, 3 host aliases, mapping to 3 host.
-        aliases = createAliases(Collections.singletonList("node4"));
+        aliases = createAliases(List.of("node4"));
         map = allocate(hostProvisioner, aliases);
         assertEquals(3, map.size());
         assertCorrectNumberOfHosts(map, 3);
diff --git a/config-model/src/test/java/com/yahoo/config/model/provision/SingleNodeProvisionerTest.java b/config-model/src/test/java/com/yahoo/config/model/provision/SingleNodeProvisionerTest.java
index e5dca4e5adf..b4f586e3f2f 100644
--- a/config-model/src/test/java/com/yahoo/config/model/provision/SingleNodeProvisionerTest.java
+++ b/config-model/src/test/java/com/yahoo/config/model/provision/SingleNodeProvisionerTest.java
@@ -12,7 +12,6 @@ import org.xml.sax.SAXException;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -40,7 +39,7 @@ public class SingleNodeProvisionerTest {
         assertTrue(map.keySet().containsAll(aliases));
 
         // 5 services, 3 host aliases, mapping to 2 host.
-        aliases = createAliases(Collections.singletonList("node3"));
+        aliases = createAliases(List.of("node3"));
         map = allocate(hostProvisioner, aliases);
 
         assertCorrectNumberOfHost(map, 1);
@@ -48,7 +47,7 @@ public class SingleNodeProvisionerTest {
         assertTrue(map.keySet().containsAll(aliases));
 
         // 5 services, 3 host aliases, mapping to 3 host.
-        aliases = createAliases(Collections.singletonList("node4"));
+        aliases = createAliases(List.of("node4"));
         map = allocate(hostProvisioner, aliases);
         assertThat(map.size(), is(3));
         assertCorrectNumberOfHost(map, 1);
diff --git a/config-model/src/test/java/com/yahoo/schema/DocumentGraphValidatorTest.java b/config-model/src/test/java/com/yahoo/schema/DocumentGraphValidatorTest.java
index defc7e59080..88761fc5d3f 100644
--- a/config-model/src/test/java/com/yahoo/schema/DocumentGraphValidatorTest.java
+++ b/config-model/src/test/java/com/yahoo/schema/DocumentGraphValidatorTest.java
@@ -9,7 +9,6 @@ import com.yahoo.schema.document.TemporarySDField;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -142,14 +141,13 @@ public class DocumentGraphValidatorTest {
         Schema campaignSchema = new Schema(name, MockApplicationPackage.createEmpty());
         SDDocumentType document = new SDDocumentType(name);
         campaignSchema.addDocument(document);
-        document.setDocumentReferences(new DocumentReferences(Collections.emptyMap()));
+        document.setDocumentReferences(new DocumentReferences(Map.of()));
         Arrays.stream(parents)
                 .map(Schema::getDocument)
                 .forEach(document::inherit);
         return campaignSchema;
     }
 
-    @SuppressWarnings("deprecation")
     private static void createDocumentReference(Schema from, Schema to, String refFieldName) {
         SDDocumentType fromDocument = from.getDocument();
         SDField refField = new TemporarySDField(fromDocument, refFieldName, NewDocumentReferenceDataType.forDocumentName(to.getName()));
diff --git a/config-model/src/test/java/com/yahoo/schema/DocumentReferenceResolverTest.java b/config-model/src/test/java/com/yahoo/schema/DocumentReferenceResolverTest.java
index e2029df70d6..99946406344 100644
--- a/config-model/src/test/java/com/yahoo/schema/DocumentReferenceResolverTest.java
+++ b/config-model/src/test/java/com/yahoo/schema/DocumentReferenceResolverTest.java
@@ -8,10 +8,9 @@ import com.yahoo.schema.document.SDDocumentType;
 import com.yahoo.schema.document.SDField;
 import org.junit.jupiter.api.Test;
 
+import java.util.List;
 import java.util.Map;
 
-import static java.util.Arrays.asList;
-import static java.util.Collections.singletonList;
 import static org.junit.jupiter.api.Assertions.*;
 
 /**
@@ -40,7 +39,7 @@ public class DocumentReferenceResolverTest {
         fooDocument.addField(irrelevantField);
         fooSchema.addDocument(fooDocument);
 
-        DocumentReferenceResolver resolver = new DocumentReferenceResolver(asList(fooSchema, barSchema));
+        DocumentReferenceResolver resolver = new DocumentReferenceResolver(List.of(fooSchema, barSchema));
         resolver.resolveReferences(fooDocument);
         assertTrue(fooDocument.getDocumentReferences().isPresent());
 
@@ -50,7 +49,6 @@ public class DocumentReferenceResolverTest {
         assertSame(fooRefToBarField, fooReferenceMap.get("bar_ref").referenceField());
     }
 
-    @SuppressWarnings("deprecation")
     @Test
     void throws_user_friendly_exception_if_referenced_document_does_not_exist() {
         Throwable exception = assertThrows(IllegalArgumentException.class, () -> {
@@ -64,7 +62,7 @@ public class DocumentReferenceResolverTest {
             fooDocument.addField(fooRefToBarField);
             fooSchema.addDocument(fooDocument);
 
-            DocumentReferenceResolver resolver = new DocumentReferenceResolver(singletonList(fooSchema));
+            DocumentReferenceResolver resolver = new DocumentReferenceResolver(List.of(fooSchema));
             resolver.resolveReferences(fooDocument);
         });
         assertTrue(exception.getMessage().contains("Invalid document reference 'bar_ref': Could not find document type 'bar'"));
@@ -86,7 +84,7 @@ public class DocumentReferenceResolverTest {
             fooDocument.addField(fooRefToBarField);
             fooSchema.addDocument(fooDocument);
 
-            DocumentReferenceResolver resolver = new DocumentReferenceResolver(asList(fooSchema, barSchema));
+            DocumentReferenceResolver resolver = new DocumentReferenceResolver(List.of(fooSchema, barSchema));
             resolver.resolveReferences(fooDocument);
         });
         assertTrue(exception.getMessage().contains("The field 'bar_ref' is an invalid document reference. The field must be an attribute."));
diff --git a/config-model/src/test/java/com/yahoo/schema/derived/SchemaOrdererTestCase.java b/config-model/src/test/java/com/yahoo/schema/derived/SchemaOrdererTestCase.java
index 593f26eb074..f83892a7a71 100644
--- a/config-model/src/test/java/com/yahoo/schema/derived/SchemaOrdererTestCase.java
+++ b/config-model/src/test/java/com/yahoo/schema/derived/SchemaOrdererTestCase.java
@@ -18,7 +18,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 
-import static java.util.Collections.emptyMap;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
 /**
@@ -63,7 +62,7 @@ public class SchemaOrdererTestCase extends AbstractSchemaTestCase {
     private static Schema createSchema(String name, Map<String, Schema> schemas) {
         Schema schema = new Schema(name, MockApplicationPackage.createEmpty());
         SDDocumentType document = new SDDocumentType(name);
-        document.setDocumentReferences(new DocumentReferences(emptyMap()));
+        document.setDocumentReferences(new DocumentReferences(Map.of()));
         schema.addDocument(document);
         schemas.put(schema.getName(), schema);
         return schema;
@@ -74,7 +73,7 @@ public class SchemaOrdererTestCase extends AbstractSchemaTestCase {
     }
 
     private static void assertOrder(List<String> expectedSearchOrder, List<String> inputNames) {
-        inputNames.sort((a, b) -> a.compareTo(b));
+        inputNames.sort(String::compareTo);
         Map<String, Schema> schemas = createSchemas();
         List<Schema> inputSchemas = inputNames.stream()
                                               .map(schemas::get)
@@ -88,7 +87,6 @@ public class SchemaOrdererTestCase extends AbstractSchemaTestCase {
         assertEquals(expectedSearchOrder, actualSearchOrder);
     }
 
-    @SuppressWarnings("deprecation")
     private static void createDocumentReference(Schema from, Schema to, String refFieldName) {
         SDDocumentType fromDocument = from.getDocument();
         SDField refField = new TemporarySDField(fromDocument, refFieldName, NewDocumentReferenceDataType.forDocumentName(to.getName()));
diff --git a/config-model/src/test/java/com/yahoo/schema/processing/AddDataTypeAndTransformToSummaryOfImportedFieldsTest.java b/config-model/src/test/java/com/yahoo/schema/processing/AddDataTypeAndTransformToSummaryOfImportedFieldsTest.java
index f09a95b89a0..3da6f250853 100644
--- a/config-model/src/test/java/com/yahoo/schema/processing/AddDataTypeAndTransformToSummaryOfImportedFieldsTest.java
+++ b/config-model/src/test/java/com/yahoo/schema/processing/AddDataTypeAndTransformToSummaryOfImportedFieldsTest.java
@@ -19,7 +19,7 @@ import com.yahoo.vespa.documentmodel.SummaryField;
 import com.yahoo.vespa.documentmodel.SummaryTransform;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
+import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
@@ -63,7 +63,7 @@ public class AddDataTypeAndTransformToSummaryOfImportedFieldsTest {
         SDField targetField = new SDField(doc, "target_field", DataType.INT);
         DocumentReference documentReference = new DocumentReference(new Field("reference_field"), targetSchema);
         ImportedField importedField = new ImportedSimpleField(fieldName, documentReference, targetField);
-        return new ImportedFields(Collections.singletonMap(fieldName, importedField));
+        return new ImportedFields(Map.of(fieldName, importedField));
     }
 
     private static DocumentSummary createDocumentSummary(String fieldName, Schema schema) {
diff --git a/config-model/src/test/java/com/yahoo/schema/processing/RankingExpressionWithTransformerTokensTestCase.java b/config-model/src/test/java/com/yahoo/schema/processing/RankingExpressionWithTransformerTokensTestCase.java
index 9213f97fd9f..6cbd8faf3b0 100644
--- a/config-model/src/test/java/com/yahoo/schema/processing/RankingExpressionWithTransformerTokensTestCase.java
+++ b/config-model/src/test/java/com/yahoo/schema/processing/RankingExpressionWithTransformerTokensTestCase.java
@@ -19,7 +19,7 @@ import com.yahoo.searchlib.rankingexpression.evaluation.TensorValue;
 import com.yahoo.tensor.Tensor;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
+import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
@@ -94,16 +94,17 @@ public class RankingExpressionWithTransformerTokensTestCase {
         MockApplicationPackage application = (MockApplicationPackage) MockApplicationPackage.createEmpty();
         RankProfileRegistry rankProfileRegistry = new RankProfileRegistry();
         QueryProfileRegistry queryProfileRegistry = application.getQueryProfiles();
-        String sdContent = "search test {\n" +
-                "  document test {}\n" +
-                "  rank-profile my_profile inherits default {}\n" +
-                "}";
+        String sdContent = """
+                search test {
+                  document test {}
+                  rank-profile my_profile inherits default {}
+                }""";
         ApplicationBuilder schemaBuilder = new ApplicationBuilder(application, new MockFileRegistry(), new BaseDeployLogger(), new TestProperties(), rankProfileRegistry, queryProfileRegistry);
         schemaBuilder.addSchema(sdContent);
         schemaBuilder.build(true);
         Schema schema = schemaBuilder.getSchema();
         RankProfile rp = rankProfileRegistry.get(schema, "my_profile");
-        return new RankProfileTransformContext(rp, queryProfileRegistry, Collections.emptyMap(), null, Collections.emptyMap(), Collections.emptyMap());
+        return new RankProfileTransformContext(rp, queryProfileRegistry, Map.of(), null, Map.of(), Map.of());
     }
 
 }
diff --git a/config-model/src/test/java/com/yahoo/schema/processing/ValidateFieldTypesTest.java b/config-model/src/test/java/com/yahoo/schema/processing/ValidateFieldTypesTest.java
index be72d2b12fa..8585a206d77 100644
--- a/config-model/src/test/java/com/yahoo/schema/processing/ValidateFieldTypesTest.java
+++ b/config-model/src/test/java/com/yahoo/schema/processing/ValidateFieldTypesTest.java
@@ -18,7 +18,7 @@ import com.yahoo.vespa.documentmodel.DocumentSummary;
 import com.yahoo.vespa.documentmodel.SummaryField;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
+import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -65,7 +65,7 @@ public class ValidateFieldTypesTest {
         SDField targetField = new SDField(targetSchema.getDocument(), "target_field", dataType);
         DocumentReference documentReference = new DocumentReference(new Field("reference_field"), targetSchema);
         ImportedField importedField = new ImportedSimpleField(fieldName, documentReference, targetField);
-        return new ImportedFields(Collections.singletonMap(fieldName, importedField));
+        return new ImportedFields(Map.of(fieldName, importedField));
     }
 
     private static DocumentSummary createDocumentSummary(String fieldName, DataType dataType, Schema schema) {
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsConsumersTest.java b/config-model/src/test/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsConsumersTest.java
index 88e1ba7a1a6..94dd0f367a3 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsConsumersTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/admin/metricsproxy/MetricsConsumersTest.java
@@ -8,6 +8,8 @@ import com.yahoo.vespa.model.VespaModel;
 import com.yahoo.vespa.model.admin.monitoring.MetricsConsumer;
 import org.junit.jupiter.api.Test;
 
+import java.util.List;
+
 import static ai.vespa.metrics.set.DefaultMetrics.defaultMetricSet;
 import static ai.vespa.metrics.set.DefaultVespaMetrics.defaultVespaMetricSet;
 import static ai.vespa.metrics.set.NetworkMetrics.networkMetricSet;
@@ -21,7 +23,6 @@ import static com.yahoo.vespa.model.admin.metricsproxy.MetricsProxyModelTester.c
 import static com.yahoo.vespa.model.admin.metricsproxy.MetricsProxyModelTester.getCustomConsumer;
 import static com.yahoo.vespa.model.admin.metricsproxy.MetricsProxyModelTester.getModel;
 import static com.yahoo.vespa.model.admin.metricsproxy.MetricsProxyModelTester.servicesWithAdminOnly;
-import static java.util.Collections.singleton;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -72,7 +73,7 @@ public class MetricsConsumersTest {
     void vespa_consumer_can_be_amended_via_admin_object() {
         VespaModel model = getModel(servicesWithAdminOnly(), hosted);
         var additionalMetric = new Metric("additional-metric");
-        model.getAdmin().setAdditionalDefaultMetrics(new MetricSet("amender-metrics", singleton(additionalMetric)));
+        model.getAdmin().setAdditionalDefaultMetrics(new MetricSet("amender-metrics", List.of(additionalMetric)));
 
         ConsumersConfig config = consumersConfigFromModel(model);
         assertEquals(numMetricsForVespaConsumer + 1, config.consumer(0).metric().size());
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/application/validation/change/search/DocumentTypeChangeValidatorTest.java b/config-model/src/test/java/com/yahoo/vespa/model/application/validation/change/search/DocumentTypeChangeValidatorTest.java
index 44743c4fa3e..0e3d74a6995 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/application/validation/change/search/DocumentTypeChangeValidatorTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/application/validation/change/search/DocumentTypeChangeValidatorTest.java
@@ -15,9 +15,9 @@ import org.junit.jupiter.api.Test;
 
 import java.time.Instant;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
+import java.util.Set;
 
 import static com.yahoo.vespa.model.application.validation.change.ConfigChangeTestUtils.newRefeedAction;
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -210,8 +210,8 @@ public class DocumentTypeChangeValidatorTest {
                 new NewDocumentType.Name("mydoc"),
                 headerfields,
                 new FieldSets(Optional.empty()),
-                Collections.emptySet(),
-                Collections.emptySet());
+                Set.of(),
+                Set.of());
     }
 
 }
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/container/configserver/ConfigserverClusterTest.java b/config-model/src/test/java/com/yahoo/vespa/model/container/configserver/ConfigserverClusterTest.java
index b933d86655e..5e6863360e7 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/container/configserver/ConfigserverClusterTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/container/configserver/ConfigserverClusterTest.java
@@ -22,11 +22,9 @@ import com.yahoo.vespa.model.container.xml.ConfigServerContainerModelBuilder;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
-import java.util.stream.Collectors;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -46,7 +44,7 @@ public class ConfigserverClusterTest {
 
     @Test
     void zookeeperConfig_only_config_servers_set_hosted() {
-        TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), Collections.emptyList());
+        TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), List.of());
         ZookeeperServerConfig config = getConfig(ZookeeperServerConfig.class, testOptions);
         assertZookeeperServerProperty(config.server(), ZookeeperServerConfig.Server::hostname, "cfg1", "localhost", "cfg3");
         assertZookeeperServerProperty(config.server(), ZookeeperServerConfig.Server::id, 0, 1, 2);
@@ -57,7 +55,7 @@ public class ConfigserverClusterTest {
 
     @Test
     void zookeeperConfig_with_config_servers_and_zk_ids_hosted() {
-        TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), Arrays.asList(4, 2, 3));
+        TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), List.of(4, 2, 3));
         ZookeeperServerConfig config = getConfig(ZookeeperServerConfig.class, testOptions);
         assertZookeeperServerProperty(config.server(), ZookeeperServerConfig.Server::hostname, "cfg1", "localhost", "cfg3");
         assertZookeeperServerProperty(config.server(), ZookeeperServerConfig.Server::id, 4, 2, 3);
@@ -80,7 +78,7 @@ public class ConfigserverClusterTest {
     @Test
     void zookeeperConfig_uneven_number_of_config_servers_and_zk_ids() {
         assertThrows(IllegalArgumentException.class, () -> {
-            TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), Collections.singletonList(1));
+            TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), List.of(1));
             getConfig(ZookeeperServerConfig.class, testOptions);
         });
     }
@@ -88,7 +86,7 @@ public class ConfigserverClusterTest {
     @Test
     void zookeeperConfig_negative_zk_id() {
         assertThrows(IllegalArgumentException.class, () -> {
-            TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), Arrays.asList(1, 2, -1));
+            TestOptions testOptions = createTestOptions(Arrays.asList("cfg1", "localhost", "cfg3"), List.of(1, 2, -1));
             getConfig(ZookeeperServerConfig.class, testOptions);
         });
     }
@@ -169,7 +167,7 @@ public class ConfigserverClusterTest {
     }
 
     private static <CONFIGTYPE extends ConfigInstance> CONFIGTYPE getConfig(Class<CONFIGTYPE> clazz) {
-        return getConfig(clazz, createTestOptions(Collections.emptyList(), Collections.emptyList()));
+        return getConfig(clazz, createTestOptions(List.of(), List.of()));
     }
 
     private static <CONFIGTYPE extends ConfigInstance> CONFIGTYPE getConfig(Class<CONFIGTYPE> clazz, TestOptions testOptions) {
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/container/http/BlockFeedGlobalEndpointsFilterTest.java b/config-model/src/test/java/com/yahoo/vespa/model/container/http/BlockFeedGlobalEndpointsFilterTest.java
index 73c4075a182..3345f935e1d 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/container/http/BlockFeedGlobalEndpointsFilterTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/container/http/BlockFeedGlobalEndpointsFilterTest.java
@@ -7,7 +7,6 @@ import com.yahoo.config.model.api.ContainerEndpoint;
 import com.yahoo.vespa.config.jdisc.http.filter.RuleBasedFilterConfig;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
@@ -29,7 +28,7 @@ public class BlockFeedGlobalEndpointsFilterTest {
 
     @Test
     void does_not_setup_blocking_rule_when_endpoints_empty() {
-        var filter = new BlockFeedGlobalEndpointsFilter(Collections.emptySet(), true);
+        var filter = new BlockFeedGlobalEndpointsFilter(Set.of(), true);
         var config = getConfig(filter);
         assertEquals(0, config.rule().size());
     }
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilderTestBase.java b/config-model/src/test/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilderTestBase.java
index a066308b426..a832c54021f 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilderTestBase.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilderTestBase.java
@@ -19,8 +19,8 @@ import org.junit.jupiter.api.BeforeEach;
 import org.w3c.dom.Element;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.logging.Level;
 
 import static org.junit.jupiter.api.Assertions.assertNotNull;
@@ -88,7 +88,7 @@ public abstract class ContainerModelBuilderTestBase {
     private static void generateDefaultSearchChains(ContainerCluster<?> cluster) {
         ContainerSearch search = cluster.getSearch();
         if (search != null)
-            search.initializeSearchChains(Collections.emptyMap());
+            search.initializeSearchChains(Map.of());
     }
 
     protected ComponentsConfig componentsConfig() {
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/content/ContentClusterTest.java b/config-model/src/test/java/com/yahoo/vespa/model/content/ContentClusterTest.java
index 1ba5bebea7e..4cf950e319d 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/content/ContentClusterTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/content/ContentClusterTest.java
@@ -22,7 +22,6 @@ import com.yahoo.vespa.config.content.AllClustersBucketSpacesConfig;
 import com.yahoo.vespa.config.content.DistributionConfig;
 import com.yahoo.vespa.config.content.FleetcontrollerConfig;
 import com.yahoo.vespa.config.content.StorDistributionConfig;
-import com.yahoo.vespa.config.content.StorFilestorConfig;
 import com.yahoo.vespa.config.content.core.StorDistributormanagerConfig;
 import com.yahoo.vespa.config.content.core.StorServerConfig;
 import com.yahoo.vespa.config.search.DispatchConfig;
@@ -44,7 +43,6 @@ import com.yahoo.yolean.Exceptions;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
@@ -947,8 +945,8 @@ public class ContentClusterTest extends ContentBaseTest {
                 .properties(props);
         MockRoot root = flavor.isPresent() ?
                 ContentClusterUtils.createMockRoot(new SingleNodeProvisioner(flavor.get()),
-                        Collections.emptyList(), deployStateBuilder) :
-                ContentClusterUtils.createMockRoot(Collections.emptyList(), deployStateBuilder);
+                        List.of(), deployStateBuilder) :
+                ContentClusterUtils.createMockRoot(List.of(), deployStateBuilder);
         ContentCluster cluster = ContentClusterUtils.createCluster(clusterXml, root);
         root.freezeModelTopology();
         cluster.validate();
@@ -1104,8 +1102,8 @@ public class ContentClusterTest extends ContentBaseTest {
 
         assertEquals(2, config.cluster().size());
 
-        assertClusterHasBucketSpaceMappings(config, "foo_c", Arrays.asList("bunnies", "hares"), Collections.emptyList());
-        assertClusterHasBucketSpaceMappings(config, "bar_c", Collections.emptyList(), Collections.singletonList("rabbits"));
+        assertClusterHasBucketSpaceMappings(config, "foo_c", Arrays.asList("bunnies", "hares"), List.of());
+        assertClusterHasBucketSpaceMappings(config, "bar_c", List.of(), List.of("rabbits"));
     }
 
     @Test
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/content/GlobalDistributionValidatorTest.java b/config-model/src/test/java/com/yahoo/vespa/model/content/GlobalDistributionValidatorTest.java
index 6066a27cff5..e671a47b36c 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/content/GlobalDistributionValidatorTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/content/GlobalDistributionValidatorTest.java
@@ -11,8 +11,6 @@ import java.util.Map;
 import java.util.Set;
 import java.util.stream.Stream;
 
-import static java.util.Collections.emptyMap;
-import static java.util.Collections.emptySet;
 import static java.util.stream.Collectors.toSet;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -25,7 +23,7 @@ public class GlobalDistributionValidatorTest {
     @Test
     void validation_succeeds_on_no_documents() {
         new GlobalDistributionValidator()
-                .validate(emptyMap(), emptySet());
+                .validate(Map.of(), Set.of());
     }
 
     @Test
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/content/ReservedDocumentTypeNameValidatorTest.java b/config-model/src/test/java/com/yahoo/vespa/model/content/ReservedDocumentTypeNameValidatorTest.java
index a6fa0334668..68856fe3488 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/content/ReservedDocumentTypeNameValidatorTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/content/ReservedDocumentTypeNameValidatorTest.java
@@ -5,7 +5,6 @@ import com.yahoo.documentmodel.NewDocumentType;
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
@@ -40,7 +39,7 @@ public class ReservedDocumentTypeNameValidatorTest {
     @Test
     void exception_is_not_thrown_on_unreserved_name() {
         ReservedDocumentTypeNameValidator validator = new ReservedDocumentTypeNameValidator();
-        validator.validate(asDocTypeMapping(Collections.singletonList("foo")));
+        validator.validate(asDocTypeMapping(List.of("foo")));
     }
 
     @Test
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/content/TopologicalDocumentTypeSorterTest.java b/config-model/src/test/java/com/yahoo/vespa/model/content/TopologicalDocumentTypeSorterTest.java
index c5a645bd863..3de46f00db5 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/content/TopologicalDocumentTypeSorterTest.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/content/TopologicalDocumentTypeSorterTest.java
@@ -6,7 +6,6 @@ import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -20,24 +19,24 @@ public class TopologicalDocumentTypeSorterTest {
 
     @Test
     void require_that_types_without_references_are_returned_in_input_order() {
-        assertOrder(Arrays.asList("a"), new DocumentTypesBuilder().add("a"));
-        assertOrder(Arrays.asList("a", "c", "b"),
+        assertOrder(List.of("a"), new DocumentTypesBuilder().add("a"));
+        assertOrder(List.of("a", "c", "b"),
                 new DocumentTypesBuilder().add("a").add("c").add("b"));
     }
 
     @Test
     void require_that_types_with_references_are_sorted_in_topological_order() {
         assertOrder(Arrays.asList("b", "a"), new DocumentTypesBuilder()
-                .add("a", Arrays.asList("b"))
+                .add("a", List.of("b"))
                 .add("b"));
         assertOrder(Arrays.asList("c", "b", "a"), new DocumentTypesBuilder()
                 .add("a", Arrays.asList("b", "c"))
-                .add("b", Arrays.asList("c"))
+                .add("b", List.of("c"))
                 .add("c"));
         assertOrder(Arrays.asList("b", "a", "d", "c"), new DocumentTypesBuilder()
-                .add("a", Arrays.asList("b"))
+                .add("a", List.of("b"))
                 .add("b")
-                .add("c", Arrays.asList("d"))
+                .add("c", List.of("d"))
                 .add("d"));
     }
 
@@ -52,7 +51,7 @@ public class TopologicalDocumentTypeSorterTest {
         private final List<NewDocumentType> result = new ArrayList<>();
 
         public DocumentTypesBuilder add(String docTypeName) {
-            return add(docTypeName, Collections.emptyList());
+            return add(docTypeName, List.of());
         }
 
         public DocumentTypesBuilder add(String docTypeName, List<String> docTypeNameReferences) {
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/content/utils/ContentClusterUtils.java b/config-model/src/test/java/com/yahoo/vespa/model/content/utils/ContentClusterUtils.java
index a8c67ebf0a3..360ad19b710 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/content/utils/ContentClusterUtils.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/content/utils/ContentClusterUtils.java
@@ -16,7 +16,6 @@ import com.yahoo.vespa.model.admin.monitoring.builder.Metrics;
 import com.yahoo.vespa.model.content.cluster.ContentCluster;
 import org.w3c.dom.Document;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
 
@@ -67,7 +66,7 @@ public class ContentClusterUtils {
         ConfigModelContext context = ConfigModelContext.create(applicationType, root.getDeployState(),
                                                                null,null, root, null);
 
-        return new ContentCluster.Builder(admin).build(Collections.emptyList(), context, doc.getDocumentElement());
+        return new ContentCluster.Builder(admin).build(List.of(), context, doc.getDocumentElement());
     }
 
     public static ContentCluster createCluster(String clusterXml, List<String> schemas, DeployState.Builder deployStateBuilder) throws Exception {