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

16 files changed, 27 insertions, 40 deletions

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);
     }