replace .collect(toUnmodifiableList()) with .toList() (#84760)

Replace collect with a simipler toList call that also creates immutable
collection.

distribution/tools/launchers/src/main/java/org/elasticsearch/tools/launchers/JvmOption.java

@@ -98,7 +98,7 @@ class JvmOption {
             Stream.of("-Xshare:off"),
             Stream.of("-XX:+PrintFlagsFinal"),
             Stream.of("-version")
-        ).reduce(Stream::concat).get().collect(Collectors.toUnmodifiableList());
+        ).reduce(Stream::concat).get().toList();
         final Process process = new ProcessBuilder().command(command).start();
         final List<String> output = readLinesFromInputStream(process.getInputStream());
         final List<String> error = readLinesFromInputStream(process.getErrorStream());
@@ -119,7 +119,7 @@ class JvmOption {
 
     private static List<String> readLinesFromInputStream(final InputStream is) throws IOException {
         try (InputStreamReader isr = new InputStreamReader(is, StandardCharsets.UTF_8); BufferedReader br = new BufferedReader(isr)) {
-            return br.lines().collect(Collectors.toUnmodifiableList());
+            return br.lines().toList();
         }
     }
 }

distribution/tools/launchers/src/main/java/org/elasticsearch/tools/launchers/JvmOptionsParser.java

@@ -125,9 +125,7 @@ final class JvmOptionsParser {
         final List<String> jvmOptions = readJvmOptionsFiles(config);
 
         if (esJavaOpts != null) {
-            jvmOptions.addAll(
+            jvmOptions.addAll(Arrays.stream(esJavaOpts.split("\\s+")).filter(Predicate.not(String::isBlank)).toList());
-                Arrays.stream(esJavaOpts.split("\\s+")).filter(Predicate.not(String::isBlank)).collect(Collectors.toUnmodifiableList())
-            );
         }
 
         final List<String> substitutedJvmOptions = substitutePlaceholders(jvmOptions, Collections.unmodifiableMap(substitutions));

libs/ssl-config/src/main/java/org/elasticsearch/common/ssl/CompositeTrustConfig.java

@@ -63,10 +63,7 @@ public class CompositeTrustConfig implements SslTrustConfig {
 
     @Override
     public Collection<? extends StoredCertificate> getConfiguredCertificates() {
-        return configs.stream()
+        return configs.stream().map(SslTrustConfig::getConfiguredCertificates).flatMap(Collection::stream).toList();
-            .map(SslTrustConfig::getConfiguredCertificates)
-            .flatMap(Collection::stream)
-            .collect(Collectors.toUnmodifiableList());
     }
 
     @Override

libs/ssl-config/src/main/java/org/elasticsearch/common/ssl/KeyStoreUtil.java

@@ -28,7 +28,6 @@ import java.util.List;
 import java.util.Locale;
 import java.util.function.Function;
 import java.util.function.Predicate;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import javax.net.ssl.KeyManager;
@@ -281,10 +280,7 @@ public final class KeyStoreUtil {
                 if (certificates == null || certificates.length == 0) {
                     return List.of();
                 }
-                return Stream.of(certificates)
+                return Stream.of(certificates).filter(c -> c instanceof X509Certificate).map(X509Certificate.class::cast).toList();
-                    .filter(c -> c instanceof X509Certificate)
-                    .map(X509Certificate.class::cast)
-                    .collect(Collectors.toUnmodifiableList());
             } catch (KeyStoreException e) {
                 throw exceptionHandler.apply(e);
             }

libs/ssl-config/src/main/java/org/elasticsearch/common/ssl/PemTrustConfig.java

@@ -21,7 +21,6 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 import javax.net.ssl.TrustManagerFactory;
 import javax.net.ssl.X509ExtendedTrustManager;
@@ -87,7 +86,7 @@ public final class PemTrustConfig implements SslTrustConfig {
     }
 
     private List<Path> resolveFiles() {
-        return this.certificateAuthorities.stream().map(this::resolveFile).collect(Collectors.toUnmodifiableList());
+        return this.certificateAuthorities.stream().map(this::resolveFile).toList();
     }
 
     private Path resolveFile(String other) {

libs/ssl-config/src/main/java/org/elasticsearch/common/ssl/StoreKeyConfig.java

@@ -27,7 +27,6 @@ import java.util.Enumeration;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Function;
-import java.util.stream.Collectors;
 
 import javax.net.ssl.KeyManagerFactory;
 import javax.net.ssl.TrustManagerFactory;
@@ -121,7 +120,7 @@ public class StoreKeyConfig implements SslKeyConfig {
                 return null;
             })
             .filter(Objects::nonNull)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     @Override
@@ -136,7 +135,7 @@ public class StoreKeyConfig implements SslKeyConfig {
                 firstElement = false;
             }
             return certificates.stream();
-        }).collect(Collectors.toUnmodifiableList());
+        }).toList();
     }
 
     @Override

libs/ssl-config/src/main/java/org/elasticsearch/common/ssl/StoreTrustConfig.java

@@ -19,7 +19,6 @@ import java.util.Collection;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 import javax.net.ssl.X509ExtendedTrustManager;
 
@@ -73,7 +72,7 @@ public final class StoreTrustConfig implements SslTrustConfig {
             } else {
                 return null;
             }
-        }).filter(Objects::nonNull).collect(Collectors.toUnmodifiableList());
+        }).filter(Objects::nonNull).toList();
     }
 
     @Override

modules/kibana/src/test/java/org/elasticsearch/kibana/KibanaPluginTests.java

@@ -12,18 +12,13 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.indices.SystemIndexDescriptor;
 import org.elasticsearch.test.ESTestCase;
 
-import java.util.stream.Collectors;
-
 import static org.hamcrest.Matchers.contains;
 
 public class KibanaPluginTests extends ESTestCase {
 
     public void testKibanaIndexNames() {
         assertThat(
-            new KibanaPlugin().getSystemIndexDescriptors(Settings.EMPTY)
+            new KibanaPlugin().getSystemIndexDescriptors(Settings.EMPTY).stream().map(SystemIndexDescriptor::getIndexPattern).toList(),
-                .stream()
-                .map(SystemIndexDescriptor::getIndexPattern)
-                .collect(Collectors.toUnmodifiableList()),
             contains(".kibana_*", ".reporting-*", ".apm-agent-configuration*", ".apm-custom-link*")
         );
     }

server/src/main/java/org/elasticsearch/action/search/SearchProgressListener.java

@@ -20,7 +20,6 @@ import org.elasticsearch.search.aggregations.InternalAggregations;
 
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 import java.util.stream.StreamSupport;
 
 /**
@@ -171,12 +170,10 @@ public abstract class SearchProgressListener {
             .filter(Objects::nonNull)
             .map(SearchPhaseResult::getSearchShardTarget)
             .map(e -> new SearchShard(e.getClusterAlias(), e.getShardId()))
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     static List<SearchShard> buildSearchShards(GroupShardsIterator<SearchShardIterator> its) {
-        return StreamSupport.stream(its.spliterator(), false)
+        return StreamSupport.stream(its.spliterator(), false).map(e -> new SearchShard(e.getClusterAlias(), e.shardId())).toList();
-            .map(e -> new SearchShard(e.getClusterAlias(), e.shardId()))
-            .collect(Collectors.toUnmodifiableList());
     }
 }

server/src/main/java/org/elasticsearch/cluster/node/DiscoveryNodeRole.java

@@ -275,7 +275,7 @@ public class DiscoveryNodeRole implements Comparable<DiscoveryNodeRole> {
     static {
         final List<Field> roleFields = Arrays.stream(DiscoveryNodeRole.class.getFields())
             .filter(f -> f.getType().equals(DiscoveryNodeRole.class))
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         // this will detect duplicate role names
         final Map<String, DiscoveryNodeRole> roleMap = roleFields.stream().map(f -> {
             try {

server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java

@@ -562,10 +562,7 @@ public class ReplicationTracker extends AbstractIndexShardComponent implements L
      * Returns a list of peer recovery retention leases installed in this replication group
      */
     public List<RetentionLease> getPeerRecoveryRetentionLeases() {
-        return getRetentionLeases().leases()
+        return getRetentionLeases().leases().stream().filter(lease -> PEER_RECOVERY_RETENTION_LEASE_SOURCE.equals(lease.source())).toList();
-            .stream()
-            .filter(lease -> PEER_RECOVERY_RETENTION_LEASE_SOURCE.equals(lease.source()))
-            .collect(Collectors.toUnmodifiableList());
     }
 
     /**

server/src/main/java/org/elasticsearch/indices/AssociatedIndexDescriptor.java

@@ -15,7 +15,6 @@ import org.elasticsearch.cluster.metadata.Metadata;
 
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 /**
  * An "associated index" is an index that is related to or derived from a system
@@ -106,7 +105,7 @@ public class AssociatedIndexDescriptor implements IndexPatternMatcher {
      */
     @Override
     public List<String> getMatchingIndices(Metadata metadata) {
-        return metadata.indices().keySet().stream().filter(this::matchesIndexPattern).collect(Collectors.toUnmodifiableList());
+        return metadata.indices().keySet().stream().filter(this::matchesIndexPattern).toList();
     }
 
     /**

server/src/main/java/org/elasticsearch/indices/SystemDataStreamDescriptor.java

@@ -17,7 +17,6 @@ import org.elasticsearch.cluster.metadata.Metadata;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.indices.AssociatedIndexDescriptor.buildAutomaton;
 
@@ -91,7 +90,7 @@ public class SystemDataStreamDescriptor {
      * @return List of names of backing indices
      */
     public List<String> getBackingIndexNames(Metadata metadata) {
-        return metadata.indices().keySet().stream().filter(this.characterRunAutomaton::run).collect(Collectors.toUnmodifiableList());
+        return metadata.indices().keySet().stream().filter(this.characterRunAutomaton::run).toList();
     }
 
     public String getDescription() {

server/src/main/java/org/elasticsearch/indices/SystemIndexDescriptor.java

@@ -31,7 +31,6 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * A system index descriptor describes one or more system indices. It can match a number of indices using
@@ -400,7 +399,7 @@ public class SystemIndexDescriptor implements IndexPatternMatcher, Comparable<Sy
      */
     @Override
     public List<String> getMatchingIndices(Metadata metadata) {
-        return metadata.indices().keySet().stream().filter(this::matchesIndexPattern).collect(Collectors.toUnmodifiableList());
+        return metadata.indices().keySet().stream().filter(this::matchesIndexPattern).toList();
     }
 
     /**

server/src/main/java/org/elasticsearch/indices/SystemIndices.java

@@ -50,7 +50,6 @@ import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import static java.util.stream.Collectors.toUnmodifiableList;
 import static org.elasticsearch.tasks.TaskResultsService.TASKS_DESCRIPTOR;
 import static org.elasticsearch.tasks.TaskResultsService.TASKS_FEATURE_NAME;
 
@@ -513,7 +512,7 @@ public class SystemIndices {
             .stream()
             .flatMap(entry -> entry.getValue().getIndexDescriptors().stream().map(descriptor -> new Tuple<>(entry.getKey(), descriptor)))
             .sorted(Comparator.comparing(d -> d.v1() + ":" + d.v2().getIndexPattern())) // Consistent ordering -> consistent error message
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         List<Tuple<String, SystemDataStreamDescriptor>> sourceDataStreamDescriptorPair = sourceToFeature.entrySet()
             .stream()
             .filter(entry -> entry.getValue().getDataStreamDescriptors().isEmpty() == false)
@@ -521,7 +520,7 @@ public class SystemIndices {
                 entry -> entry.getValue().getDataStreamDescriptors().stream().map(descriptor -> new Tuple<>(entry.getKey(), descriptor))
             )
             .sorted(Comparator.comparing(d -> d.v1() + ":" + d.v2().getDataStreamName())) // Consistent ordering -> consistent error message
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
 
         // This is O(n^2) with the number of system index descriptors, and each check is quadratic with the number of states in the
         // automaton, but the absolute number of system index descriptors should be quite small (~10s at most), and the number of states
@@ -533,7 +532,7 @@ public class SystemIndices {
                     d -> overlaps(descriptorToCheck.v2(), d.v2())
                         || (d.v2().getAliasName() != null && descriptorToCheck.v2().matchesIndexPattern(d.v2().getAliasName()))
                 )
-                .collect(toUnmodifiableList());
+                .toList();
             if (descriptorsMatchingThisPattern.isEmpty() == false) {
                 throw new IllegalStateException(
                     "a system index descriptor ["
@@ -552,7 +551,7 @@ public class SystemIndices {
                     dsTuple -> descriptorToCheck.v2().matchesIndexPattern(dsTuple.v2().getDataStreamName())
                         || overlaps(descriptorToCheck.v2().getIndexPattern(), dsTuple.v2().getBackingIndexPattern())
                 )
-                .collect(toUnmodifiableList());
+                .toList();
             if (dataStreamsMatching.isEmpty() == false) {
                 throw new IllegalStateException(
                     "a system index descriptor ["

server/src/main/java/org/elasticsearch/tasks/TaskManager.java

@@ -404,7 +404,7 @@ public class TaskManager implements ClusterStateApplier {
                 ban.registerChannel(DIRECT_CHANNEL_TRACKER);
             }
         }
-        return cancellableTasks.getByParent(parentTaskId).map(t -> t.task).collect(Collectors.toUnmodifiableList());
+        return cancellableTasks.getByParent(parentTaskId).map(t -> t.task).toList();
     }
 
     /**

server/src/main/java/org/elasticsearch/timeseries/support/TimeSeriesMetrics.java

@@ -52,7 +52,6 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.function.Predicate;
 import java.util.regex.Pattern;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import static java.util.stream.Collectors.toList;
@@ -445,7 +444,7 @@ public class TimeSeriesMetrics {
         for (TimeSeriesMetricSelector selector : selectors) {
             metrics = metrics.filter(selector.asPredicate());
         }
-        return metrics.collect(Collectors.toUnmodifiableList());
+        return metrics.toList();
     }
 
     private SearchRequest searchInRange(List<String> metrics, List<TimeSeriesDimensionSelector> dimensions, long from, long to, int size) {

server/src/test/java/org/elasticsearch/common/util/MapsTests.java

@@ -48,10 +48,7 @@ public class MapsTests extends ESTestCase {
         final String key = randomValueOtherThanMany(keys::contains, () -> randomAlphaOfLength(16));
         final String value = randomAlphaOfLength(16);
         final Map<String, String> concatenation = Maps.copyMapWithAddedEntry(map, key, value);
-        assertMapEntriesAndImmutability(
+        assertMapEntriesAndImmutability(concatenation, Stream.concat(entries.stream(), Stream.of(entry(key, value))).toList());
-            concatenation,
-            Stream.concat(entries.stream(), Stream.of(entry(key, value))).collect(Collectors.toUnmodifiableList())
-        );
     }
 
     public void testAddEntryInImmutableMap() {
@@ -67,10 +64,7 @@ public class MapsTests extends ESTestCase {
         final String key = randomValueOtherThanMany(keys::contains, () -> randomAlphaOfLength(16));
         final String value = randomAlphaOfLength(16);
         final Map<String, String> add = Maps.copyMapWithAddedOrReplacedEntry(map, key, value);
-        assertMapEntriesAndImmutability(
+        assertMapEntriesAndImmutability(add, Stream.concat(entries.stream(), Stream.of(entry(key, value))).toList());
-            add,
-            Stream.concat(entries.stream(), Stream.of(entry(key, value))).collect(Collectors.toUnmodifiableList())
-        );
     }
 
     public void testReplaceEntryInImmutableMap() {
@@ -88,8 +82,7 @@ public class MapsTests extends ESTestCase {
         final Map<String, String> replaced = Maps.copyMapWithAddedOrReplacedEntry(map, key, value);
         assertMapEntriesAndImmutability(
             replaced,
-            Stream.concat(entries.stream().filter(e -> key.equals(e.getKey()) == false), Stream.of(entry(key, value)))
+            Stream.concat(entries.stream().filter(e -> key.equals(e.getKey()) == false), Stream.of(entry(key, value))).toList()
-                .collect(Collectors.toUnmodifiableList())
         );
     }
 

server/src/test/java/org/elasticsearch/common/util/iterable/IterablesTests.java

@@ -15,7 +15,6 @@ import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
 import java.util.NoSuchElementException;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import static org.hamcrest.Matchers.is;
@@ -84,7 +83,7 @@ public class IterablesTests extends ESTestCase {
         final List<String> list = Stream.generate(() -> randomAlphaOfLengthBetween(3, 9))
             .limit(randomIntBetween(10, 30))
             .distinct()
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         for (int i = 0; i < list.size(); i++) {
             final String val = list.get(i);
             assertThat(Iterables.indexOf(list, val::equals), is(i));

test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java

@@ -284,13 +284,9 @@ public abstract class ESTestCase extends LuceneTestCase {
             .filter(unsupportedTZIdsPredicate.negate())
             .filter(unsupportedZoneIdsPredicate.negate())
             .sorted()
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
 
-        JAVA_ZONE_IDS = ZoneId.getAvailableZoneIds()
+        JAVA_ZONE_IDS = ZoneId.getAvailableZoneIds().stream().filter(unsupportedZoneIdsPredicate.negate()).sorted().toList();
-            .stream()
-            .filter(unsupportedZoneIdsPredicate.negate())
-            .sorted()
-            .collect(Collectors.toUnmodifiableList());
     }
 
     @SuppressForbidden(reason = "force log4j and netty sysprops")

test/framework/src/main/java/org/elasticsearch/test/NodeRoles.java

@@ -38,10 +38,7 @@ public class NodeRoles {
     public static Settings onlyRoles(final Settings settings, final Set<DiscoveryNodeRole> roles) {
         return Settings.builder()
             .put(settings)
-            .putList(
+            .putList(NodeRoleSettings.NODE_ROLES_SETTING.getKey(), roles.stream().map(DiscoveryNodeRole::roleName).toList())
-                NodeRoleSettings.NODE_ROLES_SETTING.getKey(),
-                roles.stream().map(DiscoveryNodeRole::roleName).collect(Collectors.toUnmodifiableList())
-            )
             .build();
     }
 
@@ -57,7 +54,7 @@ public class NodeRoles {
                 .stream()
                 .filter(Predicate.not(roles::contains))
                 .map(DiscoveryNodeRole::roleName)
-                .collect(Collectors.toUnmodifiableList())
+                .toList()
         );
         return builder.build();
     }
@@ -73,7 +70,7 @@ public class NodeRoles {
             Stream.concat(NodeRoleSettings.NODE_ROLES_SETTING.get(settings).stream(), roles.stream())
                 .map(DiscoveryNodeRole::roleName)
                 .distinct()
-                .collect(Collectors.toUnmodifiableList())
+                .toList()
         );
         return builder.build();
     }

test/framework/src/main/java/org/elasticsearch/test/rest/ESRestTestCase.java

@@ -904,9 +904,7 @@ public abstract class ESRestTestCase extends ESTestCase {
         Request getShutdownStatus = new Request("GET", "_nodes/shutdown");
         Map<String, Object> statusResponse = responseAsMap(adminClient().performRequest(getShutdownStatus));
         List<Map<String, Object>> nodesArray = (List<Map<String, Object>>) statusResponse.get("nodes");
-        List<String> nodeIds = nodesArray.stream()
+        List<String> nodeIds = nodesArray.stream().map(nodeShutdownMetadata -> (String) nodeShutdownMetadata.get("node_id")).toList();
-            .map(nodeShutdownMetadata -> (String) nodeShutdownMetadata.get("node_id"))
-            .collect(Collectors.toUnmodifiableList());
         for (String nodeId : nodeIds) {
             Request deleteRequest = new Request("DELETE", "_nodes/" + nodeId + "/shutdown");
             assertOK(adminClient().performRequest(deleteRequest));

x-pack/plugin/autoscaling/src/internalClusterTest/java/org/elasticsearch/xpack/autoscaling/AutoscalingCountTestDeciderService.java

@@ -21,7 +21,6 @@ import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicInteger;
-import java.util.stream.Collectors;
 
 public class AutoscalingCountTestDeciderService implements AutoscalingDeciderService {
 
@@ -46,7 +45,7 @@ public class AutoscalingCountTestDeciderService implements AutoscalingDeciderSer
 
     @Override
     public List<DiscoveryNodeRole> roles() {
-        return DiscoveryNodeRole.roles().stream().collect(Collectors.toUnmodifiableList());
+        return DiscoveryNodeRole.roles().stream().toList();
     }
 
     @Override

x-pack/plugin/autoscaling/src/internalClusterTest/java/org/elasticsearch/xpack/autoscaling/AutoscalingSyncTestDeciderService.java

@@ -18,7 +18,6 @@ import org.elasticsearch.xpack.autoscaling.capacity.AutoscalingDeciderService;
 import java.util.List;
 import java.util.concurrent.BrokenBarrierException;
 import java.util.concurrent.CyclicBarrier;
-import java.util.stream.Collectors;
 
 public class AutoscalingSyncTestDeciderService implements AutoscalingDeciderService {
 
@@ -62,7 +61,7 @@ public class AutoscalingSyncTestDeciderService implements AutoscalingDeciderServ
 
     @Override
     public List<DiscoveryNodeRole> roles() {
-        return DiscoveryNodeRole.roles().stream().collect(Collectors.toUnmodifiableList());
+        return DiscoveryNodeRole.roles().stream().toList();
     }
 
     @Override

x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/capacity/FixedAutoscalingDeciderService.java

@@ -19,7 +19,6 @@ import org.elasticsearch.xcontent.XContentBuilder;
 import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 public class FixedAutoscalingDeciderService implements AutoscalingDeciderService {
 
@@ -72,7 +71,7 @@ public class FixedAutoscalingDeciderService implements AutoscalingDeciderService
 
     @Override
     public List<DiscoveryNodeRole> roles() {
-        return DiscoveryNodeRole.roles().stream().collect(Collectors.toUnmodifiableList());
+        return DiscoveryNodeRole.roles().stream().toList();
     }
 
     @Override

x-pack/plugin/ccr/src/internalClusterTest/java/org/elasticsearch/xpack/ccr/AutoFollowIT.java

@@ -50,7 +50,6 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import static java.util.stream.Collectors.toUnmodifiableList;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
@@ -504,7 +503,7 @@ public class AutoFollowIT extends CcrIntegTestCase {
             final String pattern = prefix + "pattern";
             putAutoFollowPatterns(pattern, new String[] { prefix + "*" });
             return pattern;
-        }).collect(toUnmodifiableList());
+        }).toList();
 
         // pick up some random pattern to pause
         final List<String> pausedAutoFollowerPatterns = randomSubsetOf(randomIntBetween(1, 3), autoFollowPatterns);

x-pack/plugin/core/src/main/java/org/elasticsearch/license/LicenseService.java

@@ -76,7 +76,7 @@ public class LicenseService extends AbstractLifecycleComponent implements Cluste
 
     public static final Setting<List<License.LicenseType>> ALLOWED_LICENSE_TYPES_SETTING = Setting.listSetting(
         "xpack.license.upload.types",
-        ALLOWABLE_UPLOAD_TYPES.stream().map(License.LicenseType::getTypeName).collect(Collectors.toUnmodifiableList()),
+        ALLOWABLE_UPLOAD_TYPES.stream().map(License.LicenseType::getTypeName).toList(),
         License.LicenseType::parse,
         LicenseService::validateUploadTypesSetting,
         Setting.Property.NodeScope
@@ -642,7 +642,7 @@ public class LicenseService extends AbstractLifecycleComponent implements Cluste
     }
 
     private static List<License.LicenseType> getAllowableUploadTypes() {
-        return Stream.of(License.LicenseType.values()).filter(t -> t != License.LicenseType.BASIC).collect(Collectors.toUnmodifiableList());
+        return Stream.of(License.LicenseType.values()).filter(t -> t != License.LicenseType.BASIC).toList();
     }
 
     private static void validateUploadTypesSetting(List<License.LicenseType> value) {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/action/XPackUsageResponse.java

@@ -14,7 +14,6 @@ import org.elasticsearch.xpack.core.XPackFeatureSet;
 import java.io.IOException;
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 public class XPackUsageResponse extends ActionResponse {
 
@@ -37,7 +36,7 @@ public class XPackUsageResponse extends ActionResponse {
         // we can only write the usages with version the coordinating node is compatible with otherwise it will not know the named writeable
         final List<XPackFeatureSet.Usage> usagesToWrite = usages.stream()
             .filter(usage -> out.getVersion().onOrAfter(usage.getMinimalSupportedVersion()))
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         writeTo(out, usagesToWrite);
     }
 

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/results/ClassificationInferenceResults.java

@@ -113,7 +113,7 @@ public class ClassificationInferenceResults extends SingleValueInferenceResults
         return featureImportances.stream()
             .sorted((l, r) -> Double.compare(r.getTotalImportance(), l.getTotalImportance()))
             .limit(numTopFeatures)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     public ClassificationInferenceResults(StreamInput in) throws IOException {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/results/RegressionInferenceResults.java

@@ -69,7 +69,7 @@ public class RegressionInferenceResults extends SingleValueInferenceResults {
         return featureImportances.stream()
             .sorted((l, r) -> Double.compare(Math.abs(r.getImportance()), Math.abs(l.getImportance())))
             .limit(numTopFeatures)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     public RegressionInferenceResults(StreamInput in) throws IOException {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/service/GetServiceAccountCredentialsNodesResponse.java

@@ -22,7 +22,6 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * Unlike index-backed service account tokens, file-backed tokens are local to the node.
@@ -67,8 +66,8 @@ public class GetServiceAccountCredentialsNodesResponse extends BaseNodesResponse
         }
         return fileTokenDistribution.entrySet()
             .stream()
-            .map(entry -> TokenInfo.fileToken(entry.getKey(), entry.getValue().stream().sorted().collect(Collectors.toUnmodifiableList())))
+            .map(entry -> TokenInfo.fileToken(entry.getKey(), entry.getValue().stream().sorted().toList()))
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     public static class Node extends BaseNodeResponse {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/service/GetServiceAccountCredentialsResponse.java

@@ -18,8 +18,6 @@ import java.io.IOException;
 import java.util.Collection;
 import java.util.List;
 
-import static java.util.stream.Collectors.toUnmodifiableList;
-
 public class GetServiceAccountCredentialsResponse extends ActionResponse implements ToXContentObject {
 
     private final String principal;
@@ -32,7 +30,7 @@ public class GetServiceAccountCredentialsResponse extends ActionResponse impleme
         GetServiceAccountCredentialsNodesResponse nodesResponse
     ) {
         this.principal = principal;
-        this.indexTokenInfos = indexTokenInfos == null ? List.of() : indexTokenInfos.stream().sorted().collect(toUnmodifiableList());
+        this.indexTokenInfos = indexTokenInfos == null ? List.of() : indexTokenInfos.stream().sorted().toList();
         this.nodesResponse = nodesResponse;
     }
 

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/GetUserPrivilegesResponse.java

@@ -221,7 +221,7 @@ public final class GetUserPrivilegesResponse extends ActionResponse {
                 builder.startArray(RoleDescriptor.Fields.FIELD_PERMISSIONS.getPreferredName());
                 final List<FieldPermissionsDefinition.FieldGrantExcludeGroup> sortedFieldSecurity = this.fieldSecurity.stream()
                     .sorted()
-                    .collect(Collectors.toUnmodifiableList());
+                    .toList();
                 for (FieldPermissionsDefinition.FieldGrantExcludeGroup group : sortedFieldSecurity) {
                     builder.startObject();
                     if (nonEmpty(group.getGrantedFields())) {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authz/accesscontrol/IndicesAccessControl.java

@@ -108,11 +108,7 @@ public class IndicesAccessControl {
     }
 
     private List<String> getIndexNames(Predicate<IndexAccessControl> predicate) {
-        return indexPermissions.entrySet()
+        return indexPermissions.entrySet().stream().filter(entry -> predicate.test(entry.getValue())).map(Map.Entry::getKey).toList();
-            .stream()
-            .filter(entry -> predicate.test(entry.getValue()))
-            .map(Map.Entry::getKey)
-            .collect(Collectors.toUnmodifiableList());
     }
 
     public enum DlsFlsUsage {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authz/permission/DocumentPermissions.java

@@ -36,7 +36,6 @@ import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.function.Function;
-import java.util.stream.Collectors;
 
 import static org.apache.lucene.search.BooleanClause.Occur.FILTER;
 import static org.apache.lucene.search.BooleanClause.Occur.SHOULD;
@@ -151,10 +150,10 @@ public final class DocumentPermissions implements CacheKey {
 
     private void evaluateQueries(DlsQueryEvaluationContext context) {
         if (queries != null && evaluatedQueries == null) {
-            evaluatedQueries = queries.stream().map(context::evaluate).collect(Collectors.toUnmodifiableList());
+            evaluatedQueries = queries.stream().map(context::evaluate).toList();
         }
         if (limitedByQueries != null && evaluatedLimitedByQueries == null) {
-            evaluatedLimitedByQueries = limitedByQueries.stream().map(context::evaluate).collect(Collectors.toUnmodifiableList());
+            evaluatedLimitedByQueries = limitedByQueries.stream().map(context::evaluate).toList();
         }
     }
 

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authz/privilege/ClusterPrivilegeResolver.java

@@ -46,7 +46,6 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.TreeMap;
-import java.util.stream.Collectors;
 
 /**
  * Translates cluster privilege names into concrete implementations
@@ -319,7 +318,7 @@ public class ClusterPrivilegeResolver {
             .stream()
             .filter(e -> e.getValue().permission().check(action, request, authentication))
             .map(Map.Entry::getKey)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     /**

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authz/privilege/IndexPrivilege.java

@@ -46,7 +46,6 @@ import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Predicate;
-import java.util.stream.Collectors;
 
 import static java.util.Map.entry;
 import static org.elasticsearch.xpack.core.security.support.Automatons.patterns;
@@ -253,10 +252,6 @@ public final class IndexPrivilege extends Privilege {
      * @see Privilege#sortByAccessLevel
      */
     public static Collection<String> findPrivilegesThatGrant(String action) {
-        return VALUES.entrySet()
+        return VALUES.entrySet().stream().filter(e -> e.getValue().predicate.test(action)).map(e -> e.getKey()).toList();
-            .stream()
-            .filter(e -> e.getValue().predicate.test(action))
-            .map(e -> e.getKey())
-            .collect(Collectors.toUnmodifiableList());
     }
 }

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ssl/SSLService.java

@@ -516,7 +516,7 @@ public class SSLService {
                     .filter(e -> e.getValue().equals(configuration))
                     .limit(2) // we only need to distinguishing between 0/1/many
                     .map(Entry::getKey)
-                    .collect(Collectors.toUnmodifiableList());
+                    .toList();
                 final String name = switch (names.size()) {
                     case 0 -> "(unknown)";
                     case 1 -> names.get(0);
@@ -637,11 +637,7 @@ public class SSLService {
                 );
             }
         } else if (settings.hasValue(enabledSetting) == false) {
-            final List<String> sslSettingNames = settings.keySet()
+            final List<String> sslSettingNames = settings.keySet().stream().filter(s -> s.startsWith(prefix)).sorted().toList();
-                .stream()
-                .filter(s -> s.startsWith(prefix))
-                .sorted()
-                .collect(Collectors.toUnmodifiableList());
             if (sslSettingNames.isEmpty() == false) {
                 throw new ElasticsearchSecurityException(
                     "invalid configuration for "

x-pack/plugin/core/src/test/java/org/elasticsearch/license/LicenseServiceTests.java

@@ -41,7 +41,6 @@ import java.util.List;
 import java.util.UUID;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.discovery.DiscoveryModule.DISCOVERY_TYPE_SETTING;
 import static org.elasticsearch.discovery.DiscoveryModule.SINGLE_NODE_DISCOVERY_TYPE;
@@ -93,7 +92,7 @@ public class LicenseServiceTests extends ESTestCase {
             randomIntBetween(1, LicenseService.ALLOWABLE_UPLOAD_TYPES.size() - 1),
             LicenseService.ALLOWABLE_UPLOAD_TYPES
         );
-        final List<String> allowedNames = allowed.stream().map(License.LicenseType::getTypeName).collect(Collectors.toUnmodifiableList());
+        final List<String> allowedNames = allowed.stream().map(License.LicenseType::getTypeName).toList();
         final Settings settings = Settings.builder().putList("xpack.license.upload.types", allowedNames).build();
         assertRegisterValidLicense(settings, randomFrom(allowed));
     }
@@ -107,7 +106,7 @@ public class LicenseServiceTests extends ESTestCase {
             randomIntBetween(1, LicenseService.ALLOWABLE_UPLOAD_TYPES.size() - 2),
             LicenseService.ALLOWABLE_UPLOAD_TYPES
         );
-        final List<String> allowedNames = allowed.stream().map(License.LicenseType::getTypeName).collect(Collectors.toUnmodifiableList());
+        final List<String> allowedNames = allowed.stream().map(License.LicenseType::getTypeName).toList();
         final Settings settings = Settings.builder().putList("xpack.license.upload.types", allowedNames).build();
         final License.LicenseType notAllowed = randomValueOtherThanMany(
             test -> allowed.contains(test),

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/LocalStateCompositeXPackPlugin.java

@@ -694,7 +694,7 @@ public class LocalStateCompositeXPackPlugin extends XPackPlugin
             .stream()
             .map(SearchPlugin::getRequestCacheKeyDifferentiator)
             .filter(Objects::nonNull)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
 
         if (differentiators.size() > 1) {
             throw new UnsupportedOperationException("Only the security SearchPlugin should provide the request cache key differentiator");

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/security/action/service/GetServiceAccountCredentialsResponseTests.java

@@ -31,7 +31,6 @@ import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
-import static java.util.stream.Collectors.toUnmodifiableList;
 import static org.hamcrest.Matchers.anEmptyMap;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
@@ -53,7 +52,7 @@ public class GetServiceAccountCredentialsResponseTests extends ESTestCase {
         final String principal = randomAlphaOfLengthBetween(3, 8) + "/" + randomAlphaOfLengthBetween(3, 8);
         final List<TokenInfo> indexTokenInfos = IntStream.range(0, randomIntBetween(0, 10))
             .mapToObj(i -> TokenInfo.indexToken(randomAlphaOfLengthBetween(3, 8)))
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         final GetServiceAccountCredentialsNodesResponse fileTokensResponse = randomGetServiceAccountFileTokensResponse();
         return new GetServiceAccountCredentialsResponse(principal, indexTokenInfos, fileTokensResponse);
     }
@@ -130,7 +129,6 @@ public class GetServiceAccountCredentialsResponseTests extends ESTestCase {
     }
 
     private List<TokenInfo> getAllTokenInfos(GetServiceAccountCredentialsResponse response) {
-        return Stream.concat(response.getNodesResponse().getFileTokenInfos().stream(), response.getIndexTokenInfos().stream())
+        return Stream.concat(response.getNodesResponse().getFileTokenInfos().stream(), response.getIndexTokenInfos().stream()).toList();
-            .collect(toUnmodifiableList());
     }
 }

x-pack/plugin/identity-provider/src/main/java/org/elasticsearch/xpack/idp/saml/sp/SamlServiceProviderDocument.java

@@ -41,7 +41,6 @@ import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.function.BiConsumer;
-import java.util.stream.Collectors;
 
 /**
  * This class models the storage of a {@link SamlServiceProvider} as an Elasticsearch document.
@@ -171,14 +170,14 @@ public class SamlServiceProviderDocument implements ToXContentObject, Writeable
                 } catch (CertificateEncodingException e) {
                     throw new ElasticsearchException("Cannot read certificate", e);
                 }
-            }).map(Base64.getEncoder()::encodeToString).collect(Collectors.toUnmodifiableList());
+            }).map(Base64.getEncoder()::encodeToString).toList();
         }
 
         private List<X509Certificate> decodeCertificates(List<String> encodedCertificates) {
             if (encodedCertificates == null || encodedCertificates.isEmpty()) {
                 return List.of();
             }
-            return encodedCertificates.stream().map(this::decodeCertificate).collect(Collectors.toUnmodifiableList());
+            return encodedCertificates.stream().map(this::decodeCertificate).toList();
         }
 
         private X509Certificate decodeCertificate(String base64Cert) {

x-pack/plugin/identity-provider/src/test/java/org/elasticsearch/xpack/idp/saml/sp/SamlServiceProviderDocumentTests.java

@@ -29,7 +29,6 @@ import java.security.cert.X509Certificate;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertToXContentEquivalent;
 import static org.hamcrest.Matchers.emptyIterable;
@@ -92,9 +91,7 @@ public class SamlServiceProviderDocumentTests extends IdpSamlTestCase {
 
     private SamlServiceProviderDocument createFullDocument() throws GeneralSecurityException, IOException {
         final List<X509Credential> credentials = readCredentials();
-        final List<X509Certificate> certificates = credentials.stream()
+        final List<X509Certificate> certificates = credentials.stream().map(X509Credential::getEntityCertificate).toList();
-            .map(X509Credential::getEntityCertificate)
-            .collect(Collectors.toUnmodifiableList());
         final List<X509Certificate> spCertificates = randomSubsetOf(certificates);
         final List<X509Certificate> idpCertificates = randomSubsetOf(certificates);
         final List<X509Certificate> idpMetadataCertificates = randomSubsetOf(certificates);

x-pack/plugin/logstash/src/test/java/org/elasticsearch/xpack/logstash/LogstashPluginTests.java

@@ -11,18 +11,13 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.indices.SystemIndexDescriptor;
 import org.elasticsearch.test.ESTestCase;
 
-import java.util.stream.Collectors;
-
 import static org.hamcrest.Matchers.contains;
 
 public class LogstashPluginTests extends ESTestCase {
 
     public void testSystemIndices() {
         assertThat(
-            new Logstash().getSystemIndexDescriptors(Settings.EMPTY)
+            new Logstash().getSystemIndexDescriptors(Settings.EMPTY).stream().map(SystemIndexDescriptor::getIndexPattern).toList(),
-                .stream()
-                .map(SystemIndexDescriptor::getIndexPattern)
-                .collect(Collectors.toUnmodifiableList()),
             contains(".logstash*")
         );
     }

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/dataframe/stats/ProgressTracker.java

@@ -13,7 +13,6 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.stream.Collectors;
 
 /**
  * Tracks progress of a data frame analytics job.
@@ -127,8 +126,6 @@ public class ProgressTracker {
     }
 
     public List<PhaseProgress> report() {
-        return Arrays.stream(phasesInOrder)
+        return Arrays.stream(phasesInOrder).map(phase -> new PhaseProgress(phase, progressPercentPerPhase.get(phase))).toList();
-            .map(phase -> new PhaseProgress(phase, progressPercentPerPhase.get(phase)))
-            .collect(Collectors.toUnmodifiableList());
     }
 }

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/type/DataTypes.java

@@ -16,7 +16,6 @@ import java.util.Locale;
 import java.util.Map;
 
 import static java.util.stream.Collectors.toMap;
-import static java.util.stream.Collectors.toUnmodifiableList;
 import static java.util.stream.Collectors.toUnmodifiableMap;
 
 public final class DataTypes {
@@ -72,7 +71,7 @@ public final class DataTypes {
         BINARY,
         OBJECT,
         NESTED
-    ).stream().sorted(Comparator.comparing(DataType::typeName)).collect(toUnmodifiableList());
+    ).stream().sorted(Comparator.comparing(DataType::typeName)).toList();
 
     private static final Map<String, DataType> NAME_TO_TYPE = TYPES.stream().collect(toUnmodifiableMap(DataType::typeName, t -> t));
 

x-pack/plugin/security/qa/operator-privileges-tests/src/javaRestTest/java/org/elasticsearch/xpack/security/operator/OperatorPrivilegesIT.java

@@ -29,7 +29,6 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
@@ -53,9 +52,7 @@ public class OperatorPrivilegesIT extends ESRestTestCase {
         getShutdownStatus.setOptions(RequestOptions.DEFAULT.toBuilder().addHeader("Authorization", OPERATOR_AUTH_HEADER));
         Map<String, Object> statusResponse = responseAsMap(adminClient().performRequest(getShutdownStatus));
         List<Map<String, Object>> nodesArray = (List<Map<String, Object>>) statusResponse.get("nodes");
-        List<String> nodeIds = nodesArray.stream()
+        List<String> nodeIds = nodesArray.stream().map(nodeShutdownMetadata -> (String) nodeShutdownMetadata.get("node_id")).toList();
-            .map(nodeShutdownMetadata -> (String) nodeShutdownMetadata.get("node_id"))
-            .collect(Collectors.toUnmodifiableList());
         for (String nodeId : nodeIds) {
             Request deleteRequest = new Request("DELETE", "_nodes/" + nodeId + "/shutdown");
             deleteRequest.setOptions(RequestOptions.DEFAULT.toBuilder().addHeader("Authorization", OPERATOR_AUTH_HEADER));

x-pack/plugin/security/qa/security-basic/src/javaRestTest/java/org/elasticsearch/xpack/security/QueryApiKeyIT.java

@@ -231,7 +231,7 @@ public class QueryApiKeyIT extends SecurityInBasicRestTestCase {
         final int total = randomIntBetween(8, 12);
         final List<String> apiKeyNames = IntStream.range(0, total)
             .mapToObj(i -> String.format(Locale.ROOT, "k-%02d", i))
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         final List<String> apiKeyIds = new ArrayList<>(total);
         for (int i = 0; i < total; i++) {
             apiKeyIds.add(createApiKey(apiKeyNames.get(i), null, authHeader).v1());
@@ -276,21 +276,21 @@ public class QueryApiKeyIT extends SecurityInBasicRestTestCase {
         // assert sort values match the field of API key information
         if ("name".equals(sortField)) {
             assertThat(
-                apiKeyInfos.stream().map(m -> (String) m.get("name")).collect(Collectors.toUnmodifiableList()),
+                apiKeyInfos.stream().map(m -> (String) m.get("name")).toList(),
-                equalTo(apiKeyInfos.stream().map(m -> (String) extractSortValues(m).get(0)).collect(Collectors.toUnmodifiableList()))
+                equalTo(apiKeyInfos.stream().map(m -> (String) extractSortValues(m).get(0)).toList())
             );
         } else {
             assertThat(
-                apiKeyInfos.stream().map(m -> (long) m.get("creation")).collect(Collectors.toUnmodifiableList()),
+                apiKeyInfos.stream().map(m -> (long) m.get("creation")).toList(),
-                equalTo(apiKeyInfos.stream().map(m -> (long) extractSortValues(m).get(0)).collect(Collectors.toUnmodifiableList()))
+                equalTo(apiKeyInfos.stream().map(m -> (long) extractSortValues(m).get(0)).toList())
             );
         }
         assertThat(
-            apiKeyInfos.stream().map(m -> (String) m.get("id")).collect(Collectors.toUnmodifiableList()),
+            apiKeyInfos.stream().map(m -> (String) m.get("id")).toList(),
             equalTo(apiKeyIds.subList(from, total))
         );
         assertThat(
-            apiKeyInfos.stream().map(m -> (String) m.get("name")).collect(Collectors.toUnmodifiableList()),
+            apiKeyInfos.stream().map(m -> (String) m.get("name")).toList(),
             equalTo(apiKeyNames.subList(from, total))
         );
 

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/action/enrollment/TransportNodeEnrollmentAction.java

@@ -81,7 +81,7 @@ public class TransportNodeEnrollmentAction extends HandledTransportAction<NodeEn
         final List<Tuple<PrivateKey, X509Certificate>> httpCaKeysAndCertificates = httpKeyConfig.getKeys()
             .stream()
             .filter(t -> t.v2().getBasicConstraints() != -1)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
 
         if (transportKeysAndCertificates.isEmpty()) {
             listener.onFailure(

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ApiKeyService.java

@@ -1260,7 +1260,7 @@ public class ApiKeyService {
                         }
                         final List<QueryApiKeyResponse.Item> apiKeyItem = Arrays.stream(searchResponse.getHits().getHits())
                             .map(ApiKeyService::convertSearchHitToQueryItem)
-                            .collect(Collectors.toUnmodifiableList());
+                            .toList();
                         listener.onResponse(new QueryApiKeyResponse(total, apiKeyItem));
                     }, listener::onFailure)
                 )

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/Realms.java

@@ -167,7 +167,7 @@ public class Realms implements Iterable<Realm> {
         }
 
         // Otherwise, we return anything in "all realms" that is not in the allowed realm list
-        return allConfiguredRealms.stream().filter(r -> activeSnapshot.contains(r) == false).collect(Collectors.toUnmodifiableList());
+        return allConfiguredRealms.stream().filter(r -> activeSnapshot.contains(r) == false).toList();
     }
 
     public Stream<Realm> stream() {
@@ -181,7 +181,7 @@ public class Realms implements Iterable<Realm> {
 
     // Protected for testing
     protected List<Realm> calculateLicensedRealms(XPackLicenseState licenseStateSnapshot) {
-        return allConfiguredRealms.stream().filter(r -> checkLicense(r, licenseStateSnapshot)).collect(Collectors.toUnmodifiableList());
+        return allConfiguredRealms.stream().filter(r -> checkLicense(r, licenseStateSnapshot)).toList();
     }
 
     private static boolean checkLicense(Realm realm, XPackLicenseState licenseState) {

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ldap/ActiveDirectoryGroupsResolver.java

@@ -72,7 +72,7 @@ class ActiveDirectoryGroupsResolver implements GroupsResolver {
                     Math.toIntExact(timeout.seconds()),
                     ignoreReferralErrors,
                     ActionListener.wrap((results) -> {
-                        List<String> groups = results.stream().map(SearchResultEntry::getDN).collect(Collectors.toUnmodifiableList());
+                        List<String> groups = results.stream().map(SearchResultEntry::getDN).toList();
                         listener.onResponse(groups);
                     }, listener::onFailure),
                     SearchRequest.NO_ATTRIBUTES

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ldap/SearchGroupsResolver.java

@@ -24,7 +24,6 @@ import org.elasticsearch.xpack.security.authc.ldap.support.LdapSession.GroupsRes
 
 import java.util.Collection;
 import java.util.List;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.common.Strings.isNullOrEmpty;
 import static org.elasticsearch.xpack.core.security.authc.ldap.support.SessionFactorySettings.IGNORE_REFERRAL_ERRORS_SETTING;
@@ -79,9 +78,7 @@ class SearchGroupsResolver implements GroupsResolver {
                         Math.toIntExact(timeout.seconds()),
                         ignoreReferralErrors,
                         ActionListener.wrap(
-                            (results) -> listener.onResponse(
+                            (results) -> listener.onResponse(results.stream().map((r) -> r.getDN()).toList()),
-                                results.stream().map((r) -> r.getDN()).collect(Collectors.toUnmodifiableList())
-                            ),
                             listener::onFailure
                         ),
                         SearchRequest.NO_ATTRIBUTES

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ldap/UserAttributeGroupsResolver.java

@@ -21,7 +21,6 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.xpack.core.security.authc.ldap.support.SessionFactorySettings.IGNORE_REFERRAL_ERRORS_SETTING;
 import static org.elasticsearch.xpack.security.authc.ldap.support.LdapUtils.OBJECT_CLASS_PRESENCE_FILTER;
@@ -57,7 +56,7 @@ class UserAttributeGroupsResolver implements GroupsResolver {
             final List<String> groups = attributes.stream()
                 .filter((attr) -> attr.getName().equals(attribute))
                 .flatMap(attr -> Arrays.stream(attr.getValues()))
-                .collect(Collectors.toUnmodifiableList());
+                .toList();
             listener.onResponse(groups);
         } else {
             searchForEntry(

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/saml/SamlAttributes.java

@@ -13,7 +13,6 @@ import org.opensaml.saml.saml2.core.NameIDType;
 
 import java.util.List;
 import java.util.Objects;
-import java.util.stream.Collectors;
 
 /**
  * An lightweight collection of SAML attributes
@@ -52,7 +51,7 @@ public class SamlAttributes {
         return attributes.stream()
             .filter(attr -> attributeId.equals(attr.name) || attributeId.equals(attr.friendlyName))
             .flatMap(attr -> attr.values.stream())
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     List<SamlAttribute> attributes() {
@@ -81,11 +80,7 @@ public class SamlAttributes {
             this(
                 attribute.getName(),
                 attribute.getFriendlyName(),
-                attribute.getAttributeValues()
+                attribute.getAttributeValues().stream().map(x -> x.getDOM().getTextContent()).filter(Objects::nonNull).toList()
-                    .stream()
-                    .map(x -> x.getDOM().getTextContent())
-                    .filter(Objects::nonNull)
-                    .collect(Collectors.toUnmodifiableList())
             );
         }
 

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/saml/SamlRealm.java

@@ -905,7 +905,7 @@ public final class SamlRealm extends Realm implements Releasable {
                                 return null;
                             }
                             return value;
-                        }).filter(Objects::nonNull).collect(Collectors.toUnmodifiableList())
+                        }).filter(Objects::nonNull).toList()
                     );
                 } else {
                     return new AttributeParser(

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/service/FileServiceAccountTokenStore.java

@@ -39,7 +39,6 @@ import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.stream.Collectors;
 
 public class FileServiceAccountTokenStore extends CachingServiceAccountTokenStore {
 
@@ -103,7 +102,7 @@ public class FileServiceAccountTokenStore extends CachingServiceAccountTokenStor
                     List.of(clusterService.localNode().getName())
                 )
             )
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
     }
 
     public void addListener(Runnable listener) {

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/enrollment/BaseEnrollmentTokenGenerator.java

@@ -85,8 +85,8 @@ public class BaseEnrollmentTokenGenerator {
         };
         localAddresses.sort(ipv4BeforeIpv6Comparator);
         nonLocalAddresses.sort(ipv4BeforeIpv6Comparator);
-        final List<String> distinctLocalAddresses = localAddresses.stream().distinct().collect(Collectors.toUnmodifiableList());
+        final List<String> distinctLocalAddresses = localAddresses.stream().distinct().toList();
-        final List<String> distinctNonLocalAddresses = nonLocalAddresses.stream().distinct().collect(Collectors.toUnmodifiableList());
+        final List<String> distinctNonLocalAddresses = nonLocalAddresses.stream().distinct().toList();
         return new Tuple<>(distinctLocalAddresses, distinctNonLocalAddresses);
     }
 

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/action/apikey/TransportQueryApiKeyActionTests.java

@@ -16,7 +16,6 @@ import org.elasticsearch.test.ESTestCase;
 
 import java.util.List;
 import java.util.Set;
-import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
 import static org.hamcrest.Matchers.equalTo;
@@ -35,9 +34,7 @@ public class TransportQueryApiKeyActionTests extends ESTestCase {
             "metadata." + randomAlphaOfLengthBetween(3, 8)
         );
 
-        final List<FieldSortBuilder> originals = fieldNames.stream()
+        final List<FieldSortBuilder> originals = fieldNames.stream().map(this::randomFieldSortBuilderWithName).toList();
-            .map(this::randomFieldSortBuilderWithName)
-            .collect(Collectors.toUnmodifiableList());
 
         final SearchSourceBuilder searchSourceBuilder = SearchSourceBuilder.searchSource();
         TransportQueryApiKeyAction.translateFieldSortBuilders(originals, searchSourceBuilder);

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/service/ServiceAccountServiceTests.java

@@ -53,7 +53,6 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
-import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
@@ -644,7 +643,7 @@ public class ServiceAccountServiceTests extends ESTestCase {
         final List<TokenInfo> indexTokenInfos = IntStream.range(0, randomIntBetween(0, 3))
             .mapToObj(i -> TokenInfo.indexToken(ValidationTests.randomTokenName()))
             .sorted()
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
 
         doAnswer(inv -> {
             final Object[] args = inv.getArguments();

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/support/ApiKeyBoolQueryBuilderTests.java

@@ -35,7 +35,6 @@ import java.time.Instant;
 import java.time.temporal.ChronoUnit;
 import java.util.List;
 import java.util.function.Predicate;
-import java.util.stream.Collectors;
 
 import static org.elasticsearch.xpack.security.support.ApiKeyFieldNameTranslators.FIELD_NAME_TRANSLATORS;
 import static org.hamcrest.Matchers.containsString;
@@ -311,7 +310,7 @@ public class ApiKeyBoolQueryBuilderTests extends ESTestCase {
             .stream()
             .filter(q -> q.getClass() == TermQueryBuilder.class)
             .map(q -> (TermQueryBuilder) q)
-            .collect(Collectors.toUnmodifiableList());
+            .toList();
         assertTrue(tqb.stream().anyMatch(q -> q.equals(QueryBuilders.termQuery("doc_type", "api_key"))));
         if (authentication == null) {
             return;

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/type/SqlDataTypes.java

@@ -27,7 +27,6 @@ import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import static java.util.Collections.unmodifiableMap;
-import static java.util.stream.Collectors.toUnmodifiableList;
 import static java.util.stream.Collectors.toUnmodifiableMap;
 import static org.elasticsearch.xpack.ql.type.DataTypes.BINARY;
 import static org.elasticsearch.xpack.ql.type.DataTypes.BOOLEAN;
@@ -163,7 +162,7 @@ public class SqlDataTypes {
             GEO_POINT,
             SHAPE
         )
-    ).sorted(Comparator.comparing(DataType::typeName)).collect(toUnmodifiableList());
+    ).sorted(Comparator.comparing(DataType::typeName)).toList();
 
     private static final Map<String, DataType> NAME_TO_TYPE = TYPES.stream().collect(toUnmodifiableMap(DataType::typeName, t -> t));
 

x-pack/plugin/stack/src/main/java/org/elasticsearch/xpack/stack/StackTemplateRegistry.java

@@ -30,7 +30,6 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 public class StackTemplateRegistry extends IndexTemplateRegistry {
@@ -127,7 +126,7 @@ public class StackTemplateRegistry extends IndexTemplateRegistry {
         new LifecyclePolicyConfig(ILM_90_DAYS_POLICY_NAME, "/" + ILM_90_DAYS_POLICY_NAME + ".json"),
         new LifecyclePolicyConfig(ILM_180_DAYS_POLICY_NAME, "/" + ILM_180_DAYS_POLICY_NAME + ".json"),
         new LifecyclePolicyConfig(ILM_365_DAYS_POLICY_NAME, "/" + ILM_365_DAYS_POLICY_NAME + ".json")
-    ).map(config -> config.load(LifecyclePolicyConfig.DEFAULT_X_CONTENT_REGISTRY)).collect(Collectors.toUnmodifiableList());
+    ).map(config -> config.load(LifecyclePolicyConfig.DEFAULT_X_CONTENT_REGISTRY)).toList();
 
     @Override
     protected List<LifecyclePolicy> getPolicyConfigs() {