Unify on List.of

16 files changed, 33 insertions, 48 deletions

diff --git a/container-search/src/main/java/com/yahoo/search/Query.java b/container-search/src/main/java/com/yahoo/search/Query.java
index 3227b047984..4ec3fa358d2 100644
--- a/container-search/src/main/java/com/yahoo/search/Query.java
+++ b/container-search/src/main/java/com/yahoo/search/Query.java
@@ -772,7 +772,7 @@ public class Query extends com.yahoo.processing.Request implements Cloneable {
 
     private String serializeSortingAndLimits(boolean includeHitsAndOffset) {
         StringBuilder insert = new StringBuilder();
-        if (getRanking().getSorting() != null && getRanking().getSorting().fieldOrders().size() > 0) {
+        if (getRanking().getSorting() != null && !getRanking().getSorting().fieldOrders().isEmpty()) {
             serializeSorting(insert);
         }
         if (includeHitsAndOffset) {
diff --git a/container-search/src/main/java/com/yahoo/search/dispatch/InvokerResult.java b/container-search/src/main/java/com/yahoo/search/dispatch/InvokerResult.java
index 88d6b68a610..9c41c0b930f 100644
--- a/container-search/src/main/java/com/yahoo/search/dispatch/InvokerResult.java
+++ b/container-search/src/main/java/com/yahoo/search/dispatch/InvokerResult.java
@@ -7,7 +7,6 @@ import com.yahoo.search.Result;
 import com.yahoo.search.query.Sorting;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 /**
@@ -22,7 +21,7 @@ public class InvokerResult {
 
     public InvokerResult(Result result) {
         this.result = result;
-        this.leanHits = Collections.emptyList();
+        this.leanHits = List.of();
     }
 
     public InvokerResult(Query query, int expectedHits) {
@@ -54,7 +53,8 @@ public class InvokerResult {
             fh.setCached(false);
             result.hits().add(fh);
         }
-        leanHits.clear();
+        if (!leanHits.isEmpty())
+            leanHits.clear();
     }
 
 }
diff --git a/container-search/src/main/java/com/yahoo/search/dispatch/SearchPath.java b/container-search/src/main/java/com/yahoo/search/dispatch/SearchPath.java
index 9302ce5b7c6..add562bd5ad 100644
--- a/container-search/src/main/java/com/yahoo/search/dispatch/SearchPath.java
+++ b/container-search/src/main/java/com/yahoo/search/dispatch/SearchPath.java
@@ -8,7 +8,6 @@ import com.yahoo.search.dispatch.searchcluster.Node;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Optional;
@@ -163,7 +162,7 @@ public class SearchPath {
                 nodes = parseNodeRange(nodes, ret);
             } else {
                 if (isWildcard(nodes)) { // any node will be accepted
-                    return Collections.emptyList();
+                    return List.of();
                 }
                 nodes = parseNodeNum(nodes, ret);
             }
@@ -231,7 +230,7 @@ public class SearchPath {
 
         public Collection<Integer> matches(int max) {
             if (from >= max) {
-                return Collections.emptyList();
+                return List.of();
             }
             int end = Math.min(to, max);
             return IntStream.range(from, end).boxed().toList();
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/GroupingQueryParser.java b/container-search/src/main/java/com/yahoo/search/grouping/GroupingQueryParser.java
index 3ad610f6ee0..da0b258d6ef 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/GroupingQueryParser.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/GroupingQueryParser.java
@@ -15,7 +15,6 @@ import com.yahoo.search.query.Select;
 import com.yahoo.search.searchchain.Execution;
 import com.yahoo.search.searchchain.PhaseNames;
 
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
@@ -83,7 +82,7 @@ public class GroupingQueryParser extends Searcher {
 
     private List<Continuation> getContinuations(String param) {
         if (param == null) {
-            return Collections.emptyList();
+            return List.of();
         }
         List<Continuation> ret = new LinkedList<>();
         for (String str : param.split(" ")) {
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/UniqueGroupingSearcher.java b/container-search/src/main/java/com/yahoo/search/grouping/UniqueGroupingSearcher.java
index 6d2b416700a..e319740f741 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/UniqueGroupingSearcher.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/UniqueGroupingSearcher.java
@@ -27,7 +27,6 @@ import com.yahoo.search.searchchain.Execution;
 import com.yahoo.search.searchchain.PhaseNames;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.logging.Logger;
 
@@ -188,7 +187,7 @@ public class UniqueGroupingSearcher extends Searcher {
     private static List<Hit> getRequestedHits(GroupList resultGroups, int offset, int hits) {
         List<Hit> receivedHits = getAllHitsFromGroupingResult(resultGroups);
         if (receivedHits.size() <= offset) {
-            return Collections.emptyList(); // There weren't any hits as far out as requested.
+            return List.of(); // There weren't any hits as far out as requested.
         }
         int lastRequestedHit = Math.min(offset + hits, receivedHits.size());
         return receivedHits.subList(offset, lastRequestedHit);
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingOperation.java b/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingOperation.java
index b6fc0ffb968..fe49b46fc6f 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingOperation.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/request/GroupingOperation.java
@@ -537,12 +537,7 @@ public abstract class GroupingOperation extends GroupingNode {
         } else if (level == 1) {
             return "single group";
         } else {
-            StringBuilder ret = new StringBuilder();
-            for (int i = 1; i < level; ++i) {
-                ret.append("list of ");
-            }
-            ret.append("groups");
-            return ret.toString();
+            return "list of ".repeat(level - 1) + "groups";
         }
     }
 
@@ -571,8 +566,8 @@ public abstract class GroupingOperation extends GroupingNode {
      * @throws IllegalArgumentException thrown if the string could not be parsed
      */
     public static List<GroupingOperation> fromStringAsList(String string) {
-        if (string == null || string.trim().length() == 0) {
-            return Collections.emptyList();
+        if (string == null || string.trim().isEmpty()) {
+            return List.of();
         }
         GroupingParserInput input = new GroupingParserInput(string);
         try {
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/request/NowFunction.java b/container-search/src/main/java/com/yahoo/search/grouping/request/NowFunction.java
index 7026e726675..a2e2bcd649a 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/request/NowFunction.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/request/NowFunction.java
@@ -1,8 +1,7 @@
 // Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.search.grouping.request;
 
-import java.util.Arrays;
-import java.util.Collections;
+import java.util.List;
 
 /**
  * This class represents a now-function in a {@link GroupingExpression}. It evaluates to a long that equals the number
@@ -21,7 +20,7 @@ public class NowFunction extends FunctionNode {
     }
 
     private NowFunction(String label, Integer level) {
-        super("now", label, level, Collections.emptyList());
+        super("now", label, level, List.of());
     }
 
     @Override
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/vespa/GroupingExecutor.java b/container-search/src/main/java/com/yahoo/search/grouping/vespa/GroupingExecutor.java
index be4f2f786e5..fba9064298c 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/vespa/GroupingExecutor.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/vespa/GroupingExecutor.java
@@ -21,7 +21,6 @@ import com.yahoo.search.searchchain.Execution;
 import com.yahoo.searchlib.aggregation.Grouping;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
@@ -357,7 +356,7 @@ public class GroupingExecutor extends Searcher {
     public static List<Grouping> getGroupingList(Query query) {
         Object obj = query.properties().get(PROP_GROUPINGLIST);
         if (!(obj instanceof List)) {
-            return Collections.emptyList();
+            return List.of();
         }
         return (List<Grouping>)obj;
     }
diff --git a/container-search/src/main/java/com/yahoo/search/pagetemplates/PageTemplateSearcher.java b/container-search/src/main/java/com/yahoo/search/pagetemplates/PageTemplateSearcher.java
index e07b290f66e..6504949e174 100644
--- a/container-search/src/main/java/com/yahoo/search/pagetemplates/PageTemplateSearcher.java
+++ b/container-search/src/main/java/com/yahoo/search/pagetemplates/PageTemplateSearcher.java
@@ -23,7 +23,6 @@ import com.yahoo.search.searchchain.Execution;
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -145,7 +144,7 @@ public class PageTemplateSearcher extends Searcher {
         // If none set, just return the default or null if none
         if (pageIds == null) {
             PageElement defaultPage=templateRegistry.getComponent("default");
-            return (defaultPage == null ? Collections.<PageElement>emptyList() : Collections.singletonList(defaultPage));
+            return (defaultPage == null ? List.of() : List.of(defaultPage));
         }
 
         // Resolve the id list to page templates
diff --git a/container-search/src/main/java/com/yahoo/search/pagetemplates/config/PageTemplateXMLReader.java b/container-search/src/main/java/com/yahoo/search/pagetemplates/config/PageTemplateXMLReader.java
index 7b969404984..d8cfaab7cba 100644
--- a/container-search/src/main/java/com/yahoo/search/pagetemplates/config/PageTemplateXMLReader.java
+++ b/container-search/src/main/java/com/yahoo/search/pagetemplates/config/PageTemplateXMLReader.java
@@ -72,7 +72,7 @@ public class PageTemplateXMLReader {
             File file = new File(fileName);
             pageReader = new NamedReader(fileName,new FileReader(file));
             String firstName = file.getName().substring(0, file.getName().length() - 4);
-            return read(Collections.singletonList(pageReader), true).getComponent(firstName);
+            return read(List.of(pageReader), true).getComponent(firstName);
         }
         catch (IOException e) {
             throw new IllegalArgumentException("Could not read the page template '" + fileName + "'", e);
@@ -296,7 +296,7 @@ public class PageTemplateXMLReader {
             if ("item".equals(value.getNodeName()))
                 map.values().add(readPageElements(value));
             else
-                map.values().add(Collections.singletonList(readPageElement(value)));
+                map.values().add(List.of(readPageElement(value)));
         }
         return map;
     }
@@ -311,7 +311,7 @@ public class PageTemplateXMLReader {
             else if (alternative.getNodeName().equals("include")) // Implicit include
                 choice.alternatives().add(readInclude(alternative));
             else // Other implicit
-                choice.alternatives().add(Collections.singletonList(readPageElement(alternative)));
+                choice.alternatives().add(List.of(readPageElement(alternative)));
         }
         return choice;
     }
@@ -323,7 +323,7 @@ public class PageTemplateXMLReader {
                 if ("alternative".equals(alternative.getNodeName())) // Explicit alternative container
                     source.renderer().alternatives().addAll(readRenderers(XML.children(alternative)));
                 else // Implicit alternative - yes implicit and explicit may be combined
-                    source.renderer().alternatives().addAll(readRenderers(Collections.singletonList(alternative)));
+                    source.renderer().alternatives().addAll(readRenderers(List.of(alternative)));
             }
         }
     }
diff --git a/container-search/src/main/java/com/yahoo/search/query/Select.java b/container-search/src/main/java/com/yahoo/search/query/Select.java
index 32e28dc3ff7..6735a6bd050 100644
--- a/container-search/src/main/java/com/yahoo/search/query/Select.java
+++ b/container-search/src/main/java/com/yahoo/search/query/Select.java
@@ -10,7 +10,6 @@ import com.yahoo.search.query.profile.types.QueryProfileType;
 import com.yahoo.search.yql.VespaGroupingStep;
 
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
@@ -53,7 +52,7 @@ public class Select implements Cloneable {
     }
 
     public Select(String where, String grouping, Query query) {
-        this(where, grouping, null, query, Collections.emptyList());
+        this(where, grouping, null, query, List.of());
     }
 
     private Select(String where, String grouping, String groupingExpressionString, Query query, List<GroupingRequest> groupingRequests) {
diff --git a/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfile.java b/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfile.java
index 1c694417475..d638f57422c 100644
--- a/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfile.java
+++ b/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfile.java
@@ -121,7 +121,7 @@ public class QueryProfile extends FreezableSimpleComponent implements Cloneable
      */
     public List<QueryProfile> inherited() {
         if (isFrozen()) return inherited; // Frozen profiles always have an unmodifiable, non-null list
-        if (inherited == null) return Collections.emptyList();
+        if (inherited == null) return List.of();
         return Collections.unmodifiableList(inherited);
     }
 
diff --git a/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfileVariants.java b/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfileVariants.java
index 0ed6b590227..c9dbfe9d89a 100644
--- a/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfileVariants.java
+++ b/container-search/src/main/java/com/yahoo/search/query/profile/QueryProfileVariants.java
@@ -5,7 +5,6 @@ import com.yahoo.component.provider.Freezable;
 import com.yahoo.search.query.profile.types.QueryProfileType;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -187,7 +186,7 @@ public class QueryProfileVariants implements Freezable, Cloneable {
      * @param dimensionBinding the dimension bindings to use in this
      */
     public Object get(String name, QueryProfileType type, boolean allowQueryProfileResult, DimensionBinding dimensionBinding) {
-        SingleValueQueryProfileVisitor visitor = new SingleValueQueryProfileVisitor(Collections.singletonList(name),allowQueryProfileResult);
+        SingleValueQueryProfileVisitor visitor = new SingleValueQueryProfileVisitor(List.of(name),allowQueryProfileResult);
         visitor.enter("");
         accept(true, type, visitor, dimensionBinding);
         visitor.leave("");
@@ -370,7 +369,7 @@ public class QueryProfileVariants implements Freezable, Cloneable {
 
         /** Returns the field values (values for various dimensions) for this field as a read-only list (never null) */
         public List<FieldValue> asList() {
-            if (resolutionList == null) return Collections.emptyList();
+            if (resolutionList == null) return List.of();
             return resolutionList;
         }
 
diff --git a/container-search/src/main/java/com/yahoo/search/rendering/RendererRegistry.java b/container-search/src/main/java/com/yahoo/search/rendering/RendererRegistry.java
index d62860afcda..74e79475ce6 100644
--- a/container-search/src/main/java/com/yahoo/search/rendering/RendererRegistry.java
+++ b/container-search/src/main/java/com/yahoo/search/rendering/RendererRegistry.java
@@ -10,7 +10,7 @@ import com.yahoo.search.Result;
 import com.yahoo.search.pagetemplates.result.PageTemplatesXmlRenderer;
 
 import java.util.Collection;
-import java.util.Collections;
+import java.util.List;
 import java.util.concurrent.Executor;
 
 /**
@@ -34,7 +34,7 @@ public final class RendererRegistry extends ComponentRegistry<com.yahoo.processi
      * Use MoreExecutors.directExecutor().
      */
     public RendererRegistry(Executor executor) {
-        this(Collections.emptyList(), executor);
+        this(List.of(), executor);
     }
 
     /** 
@@ -111,7 +111,7 @@ public final class RendererRegistry extends ComponentRegistry<com.yahoo.processi
     private String rendererNames() {
         StringBuilder r = new StringBuilder();
         for (Renderer<Result> c : allComponents()) {
-            if (r.length() > 0)
+            if (!r.isEmpty())
                 r.append(", ");
             r.append(c.getId().stringValue());
         }
diff --git a/container-search/src/main/java/com/yahoo/search/rendering/SectionedRenderer.java b/container-search/src/main/java/com/yahoo/search/rendering/SectionedRenderer.java
index 6f376042f2d..7bd3ca1174f 100644
--- a/container-search/src/main/java/com/yahoo/search/rendering/SectionedRenderer.java
+++ b/container-search/src/main/java/com/yahoo/search/rendering/SectionedRenderer.java
@@ -15,7 +15,6 @@ import java.io.IOException;
 import java.io.Writer;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
 
 
@@ -156,7 +155,7 @@ abstract public class SectionedRenderer<WRITER> extends Renderer {
     }
 
     private  void renderResultContent(WRITER writer, Result result) throws IOException {
-        if (result.hits().getError() != null || result.hits().getQuery().errors().size() > 0) {
+        if (result.hits().getError() != null || !result.hits().getQuery().errors().isEmpty()) {
             error(writer, asUnmodifiableSearchErrorList(result.hits().getQuery().errors(), result.hits().getError()));
         }
 
@@ -172,14 +171,14 @@ abstract public class SectionedRenderer<WRITER> extends Renderer {
     }
 
     private Collection<ErrorMessage> asUnmodifiableSearchErrorList(List<com.yahoo.processing.request.ErrorMessage> queryErrors,ErrorMessage resultError) {
-        if (queryErrors.size() == 0)
-            return Collections.singletonList(resultError);
+        if (queryErrors.isEmpty())
+            return List.of(resultError);
         List<ErrorMessage> searchErrors = new ArrayList<>(queryErrors.size() + (resultError != null ? 1 :0) );
-        for (int i=0; i<queryErrors.size(); i++)
-            searchErrors.add(ErrorMessage.from(queryErrors.get(i)));
+        for (com.yahoo.processing.request.ErrorMessage queryError : queryErrors)
+            searchErrors.add(ErrorMessage.from(queryError));
         if (resultError != null)
             searchErrors.add(resultError);
-        return Collections.unmodifiableCollection(searchErrors);
+        return List.copyOf(searchErrors);
     }
 
     private void renderHitGroup(WRITER writer, HitGroup hitGroup) throws IOException {
diff --git a/container-search/src/main/java/com/yahoo/search/searchchain/model/VespaSearchers.java b/container-search/src/main/java/com/yahoo/search/searchchain/model/VespaSearchers.java
index f21ea506fde..69a1f8ec6cb 100644
--- a/container-search/src/main/java/com/yahoo/search/searchchain/model/VespaSearchers.java
+++ b/container-search/src/main/java/com/yahoo/search/searchchain/model/VespaSearchers.java
@@ -11,7 +11,6 @@ import com.yahoo.search.searchchain.model.federation.FederationSearcherModel;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
@@ -61,7 +60,7 @@ public class VespaSearchers {
     private static FederationSearcherModel federationSearcherModel() {
         return new FederationSearcherModel(new ComponentSpecification("federation"),
                                            Dependencies.emptyDependencies(),
-                                           Collections.emptyList(),
+                                           List.of(),
                                            true);
     }