Use Java 11 collections conveniences everywhere

client/rest-high-level/src/main/java/org/elasticsearch/client/ml/filestructurefinder/FileStructure.java

@@ -25,7 +25,6 @@
 import org.elasticsearch.common.xcontent.XContentParser;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -148,22 +147,20 @@ private FileStructure(int numLinesAnalyzed, int numMessagesAnalyzed, String samp
         this.format = Objects.requireNonNull(format);
         this.multilineStartPattern = multilineStartPattern;
         this.excludeLinesPattern = excludeLinesPattern;
-        this.columnNames = (columnNames == null) ? null : Collections.unmodifiableList(new ArrayList<>(columnNames));
+        this.columnNames = (columnNames == null) ? null : List.copyOf(columnNames);
         this.hasHeaderRow = hasHeaderRow;
         this.delimiter = delimiter;
         this.quote = quote;
         this.shouldTrimFields = shouldTrimFields;
         this.grokPattern = grokPattern;
         this.timestampField = timestampField;
-        this.jodaTimestampFormats =
-            (jodaTimestampFormats == null) ? null : Collections.unmodifiableList(new ArrayList<>(jodaTimestampFormats));
-        this.javaTimestampFormats =
-            (javaTimestampFormats == null) ? null : Collections.unmodifiableList(new ArrayList<>(javaTimestampFormats));
+        this.jodaTimestampFormats = (jodaTimestampFormats == null) ? null : List.copyOf(jodaTimestampFormats);
+        this.javaTimestampFormats = (javaTimestampFormats == null) ? null : List.copyOf(javaTimestampFormats);
         this.needClientTimezone = needClientTimezone;
         this.mappings = Collections.unmodifiableSortedMap(new TreeMap<>(mappings));
         this.ingestPipeline = (ingestPipeline == null) ? null : Collections.unmodifiableMap(new LinkedHashMap<>(ingestPipeline));
         this.fieldStats = Collections.unmodifiableSortedMap(new TreeMap<>(fieldStats));
-        this.explanation = (explanation == null) ? null : Collections.unmodifiableList(new ArrayList<>(explanation));
+        this.explanation = (explanation == null) ? null : List.copyOf(explanation);
     }
 
     public int getNumLinesAnalyzed() {

client/rest-high-level/src/main/java/org/elasticsearch/client/security/GetPrivilegesResponse.java

@@ -26,7 +26,6 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;
@@ -44,7 +43,7 @@ public Set<ApplicationPrivilege> getPrivileges() {
     }
 
     public GetPrivilegesResponse(Collection<ApplicationPrivilege> privileges) {
-        this.privileges = Collections.unmodifiableSet(new HashSet<>(privileges));
+        this.privileges = Set.copyOf(privileges);
     }
 
     public static GetPrivilegesResponse fromXContent(XContentParser parser) throws IOException {

client/rest-high-level/src/main/java/org/elasticsearch/client/security/GetUsersResponse.java

@@ -122,11 +122,11 @@ protected static final class ParsedUser {
 
         public ParsedUser(String username, Collection<String> roles, Map<String, Object> metadata, Boolean enabled,
                           @Nullable String fullName, @Nullable String email) {
-            String checkedUsername = username = Objects.requireNonNull(username, "`username` is required, cannot be null");
-            Collection<String> checkedRoles = Collections.unmodifiableSet(new HashSet<>(
-                Objects.requireNonNull(roles, "`roles` is required, cannot be null. Pass an empty Collection instead.")));
-            Map<String, Object> checkedMetadata = Collections
-                .unmodifiableMap(Objects.requireNonNull(metadata, "`metadata` is required, cannot be null. Pass an empty map instead."));
+            String checkedUsername = Objects.requireNonNull(username, "`username` is required, cannot be null");
+            Collection<String> checkedRoles =
+                    Set.copyOf(Objects.requireNonNull(roles, "`roles` is required, cannot be null. Pass an empty Collection instead."));
+            Map<String, Object> checkedMetadata = Collections.unmodifiableMap(
+                    Objects.requireNonNull(metadata, "`metadata` is required, cannot be null. Pass an empty map instead."));
             this.user = new User(checkedUsername, checkedRoles, checkedMetadata, fullName, email);
             this.enabled = enabled;
         }

client/rest-high-level/src/main/java/org/elasticsearch/client/security/support/expressiondsl/expressions/CompositeRoleMapperExpression.java

@@ -23,8 +23,6 @@
 import org.elasticsearch.common.xcontent.XContentBuilder;
 
 import java.io.IOException;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
@@ -53,7 +51,7 @@ public abstract class CompositeRoleMapperExpression implements RoleMapperExpress
         assert name != null : "field name cannot be null";
         assert elements != null : "at least one field expression is required";
         this.name = name;
-        this.elements = Collections.unmodifiableList(Arrays.asList(elements));
+        this.elements = List.of(elements);
     }
 
     public String getName() {

client/rest-high-level/src/main/java/org/elasticsearch/client/security/support/expressiondsl/fields/FieldRoleMapperExpression.java

@@ -23,8 +23,6 @@
 import org.elasticsearch.common.xcontent.XContentBuilder;
 
 import java.io.IOException;
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 
@@ -53,7 +51,7 @@ public FieldRoleMapperExpression(final String field, final Object... values) {
             throw new IllegalArgumentException("null or empty values for field (" + field + ")");
         }
         this.field = field;
-        this.values = Collections.unmodifiableList(Arrays.asList(values));
+        this.values = List.of(values);
     }
 
     public String getField() {

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/User.java

@@ -24,7 +24,6 @@
 
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -52,11 +51,10 @@ public final class User {
      */
     public User(String username, Collection<String> roles, Map<String, Object> metadata, @Nullable String fullName,
             @Nullable String email) {
-        this.username = username = Objects.requireNonNull(username, "`username` is required, cannot be null");
-        this.roles = Collections.unmodifiableSet(new HashSet<>(
-                Objects.requireNonNull(roles, "`roles` is required, cannot be null. Pass an empty Collection instead.")));
-        this.metadata = Collections
-                .unmodifiableMap(Objects.requireNonNull(metadata, "`metadata` is required, cannot be null. Pass an empty map instead."));
+        this.username = Objects.requireNonNull(username, "`username` is required, cannot be null");
+        this.roles = Set.copyOf(Objects.requireNonNull(roles, "`roles` is required, cannot be null. Pass an empty Collection instead."));
+        this.metadata = Collections.unmodifiableMap(
+                Objects.requireNonNull(metadata, "`metadata` is required, cannot be null. Pass an empty map instead."));
         this.fullName = fullName;
         this.email = email;
     }

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/AbstractIndicesPrivileges.java

@@ -31,7 +31,7 @@
 import java.io.UncheckedIOException;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
+import java.util.List;
 import java.util.Objects;
 import java.util.Set;
 
@@ -44,8 +44,8 @@ public abstract class AbstractIndicesPrivileges {
     static final ParseField FIELD_PERMISSIONS = new ParseField("field_security");
     static final ParseField QUERY = new ParseField("query");
 
-    protected final Set<String> indices;
-    protected final Set<String> privileges;
+    protected final List<String> indices;
+    protected final List<String> privileges;
     protected final boolean allowRestrictedIndices;
 
     AbstractIndicesPrivileges(Collection<String> indices, Collection<String> privileges, boolean allowRestrictedIndices) {
@@ -55,15 +55,15 @@ public abstract class AbstractIndicesPrivileges {
         if (null == privileges || privileges.isEmpty()) {
             throw new IllegalArgumentException("indices privileges must define at least one privilege");
         }
-        this.indices = Collections.unmodifiableSet(new HashSet<>(indices));
-        this.privileges = Collections.unmodifiableSet(new HashSet<>(privileges));
+        this.indices = List.copyOf(indices);
+        this.privileges = List.copyOf(privileges);
         this.allowRestrictedIndices = allowRestrictedIndices;
     }
 
     /**
      * The indices names covered by the privileges.
      */
-    public Set<String> getIndices() {
+    public List<String> getIndices() {
         return this.indices;
     }
 
@@ -72,7 +72,7 @@ public Set<String> getIndices() {
      * such privileges, but the {@code String} datatype allows for flexibility in defining
      * finer grained privileges.
      */
-    public Set<String> getPrivileges() {
+    public List<String> getPrivileges() {
         return this.privileges;
     }
 
@@ -127,9 +127,9 @@ static FieldSecurity parse(XContentParser parser, Void context) throws IOExcepti
 
         FieldSecurity(Collection<String> grantedFields, Collection<String> deniedFields) {
             // unspecified granted fields means no restriction
-            this.grantedFields = grantedFields == null ? null : Collections.unmodifiableSet(new HashSet<>(grantedFields));
+            this.grantedFields = grantedFields == null ? null : Set.copyOf(grantedFields);
             // unspecified denied fields means no restriction
-            this.deniedFields = deniedFields == null ? null : Collections.unmodifiableSet(new HashSet<>(deniedFields));
+            this.deniedFields = deniedFields == null ? null : Set.copyOf(deniedFields);
         }
 
         /**

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/ApplicationPrivilege.java

@@ -29,11 +29,9 @@
 import org.elasticsearch.common.xcontent.XContentParser;
 
 import java.io.IOException;
-
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
@@ -72,12 +70,12 @@ public ApplicationPrivilege(String application, String name, Collection<String>
         if (actions == null || actions.isEmpty()) {
             throw new IllegalArgumentException("actions must be provided");
         } else {
-            this.actions = Collections.unmodifiableSet(new HashSet<>(actions));
+            this.actions = Set.copyOf(actions);
         }
         if (metadata == null || metadata.isEmpty()) {
             this.metadata = Collections.emptyMap();
         } else {
-            this.metadata = Collections.unmodifiableMap(metadata);
+            this.metadata = Map.copyOf(metadata);
         }
     }
 

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/ApplicationResourcePrivileges.java

@@ -30,8 +30,6 @@
 
 import java.io.IOException;
 import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
 import java.util.Objects;
 import java.util.Set;
 
@@ -96,8 +94,8 @@ public ApplicationResourcePrivileges(String application, Collection<String> priv
             throw new IllegalArgumentException("application privileges must refer to at least one resource");
         }
         this.application = application;
-        this.privileges = Collections.unmodifiableSet(new HashSet<>(privileges));
-        this.resources = Collections.unmodifiableSet(new HashSet<>(resources));
+        this.privileges = Set.copyOf(privileges);
+        this.resources = Set.copyOf(resources);
     }
 
     public String getApplication() {

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/GlobalPrivileges.java

@@ -28,7 +28,6 @@
 import java.io.IOException;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -82,7 +81,7 @@ public GlobalPrivileges(Collection<? extends GlobalOperationPrivilege> privilege
             throw new IllegalArgumentException("Privileges cannot be empty or null");
         }
         // duplicates are just ignored
-        this.privileges = Collections.unmodifiableSet(new HashSet<>(Objects.requireNonNull(privileges)));
+        this.privileges = Set.copyOf(Objects.requireNonNull(privileges));
         this.privilegesByCategoryMap = Collections
                 .unmodifiableMap(this.privileges.stream().collect(Collectors.groupingBy(GlobalOperationPrivilege::getCategory)));
         for (final Map.Entry<String, List<GlobalOperationPrivilege>> privilegesByCategory : privilegesByCategoryMap.entrySet()) {

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/IndicesPrivileges.java

@@ -30,6 +30,7 @@
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.List;
 import java.util.Objects;
 
 import static org.elasticsearch.common.xcontent.ConstructingObjectParser.constructorArg;
@@ -48,8 +49,8 @@ public final class IndicesPrivileges extends AbstractIndicesPrivileges implement
     static final ConstructingObjectParser<IndicesPrivileges, Void> PARSER =
         new ConstructingObjectParser<>("indices_privileges", false, constructorObjects -> {
             int i = 0;
-            final Collection<String> indices = (Collection<String>) constructorObjects[i++];
-            final Collection<String> privileges = (Collection<String>) constructorObjects[i++];
+            final List<String> indices = (List<String>) constructorObjects[i++];
+            final List<String> privileges = (List<String>) constructorObjects[i++];
             final boolean allowRestrictedIndices = (Boolean) constructorObjects[i++];
             final FieldSecurity fields = (FieldSecurity) constructorObjects[i++];
             final String query = (String) constructorObjects[i];
@@ -68,7 +69,7 @@ public final class IndicesPrivileges extends AbstractIndicesPrivileges implement
     // missing query means all documents, i.e. no restrictions
     private final @Nullable String query;
 
-    private IndicesPrivileges(Collection<String> indices, Collection<String> privileges, boolean allowRestrictedIndices,
+    private IndicesPrivileges(List<String> indices, List<String> privileges, boolean allowRestrictedIndices,
                               @Nullable FieldSecurity fieldSecurity, @Nullable String query) {
         super(indices, privileges, allowRestrictedIndices);
         this.fieldSecurity = fieldSecurity;
@@ -165,9 +166,9 @@ public static Builder builder() {
     public static final class Builder {
 
         private @Nullable
-        Collection<String> indices = null;
+        List<String> indices = null;
         private @Nullable
-        Collection<String> privileges = null;
+        List<String> privileges = null;
         private @Nullable
         Collection<String> grantedFields = null;
         private @Nullable
@@ -183,7 +184,7 @@ public Builder indices(String... indices) {
             return indices(Arrays.asList(Objects.requireNonNull(indices, "indices required")));
         }
 
-        public Builder indices(Collection<String> indices) {
+        public Builder indices(List<String> indices) {
             this.indices = Objects.requireNonNull(indices, "indices required");
             return this;
         }
@@ -192,7 +193,7 @@ public Builder privileges(String... privileges) {
             return privileges(Arrays.asList(Objects.requireNonNull(privileges, "privileges required")));
         }
 
-        public Builder privileges(Collection<String> privileges) {
+        public Builder privileges(List<String> privileges) {
             this.privileges = Objects.requireNonNull(privileges, "privileges required");
             return this;
         }

client/rest-high-level/src/main/java/org/elasticsearch/client/security/user/privileges/UserIndicesPrivileges.java

@@ -26,7 +26,6 @@
 import java.io.IOException;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;
 import java.util.Set;
@@ -75,8 +74,8 @@ public static UserIndicesPrivileges fromXContent(XContentParser parser) throws I
     public UserIndicesPrivileges(Collection<String> indices, Collection<String> privileges, boolean allowRestrictedIndices,
                                  Collection<IndicesPrivileges.FieldSecurity> fieldSecurity, Collection<String> query) {
         super(indices, privileges, allowRestrictedIndices);
-        this.fieldSecurity = fieldSecurity == null ? Collections.emptySet() : Collections.unmodifiableSet(new HashSet<>(fieldSecurity));
-        this.query = query == null ? Collections.emptySet() : Collections.unmodifiableSet(new HashSet<>(query));
+        this.fieldSecurity = fieldSecurity == null ? Collections.emptySet() : Set.copyOf(fieldSecurity);
+        this.query = query == null ? Collections.emptySet() : Set.copyOf(query);
     }
 
     public Set<IndicesPrivileges.FieldSecurity> getFieldSecurity() {

client/transport/src/main/java/org/elasticsearch/transport/client/PreBuiltTransportClient.java

@@ -21,7 +21,6 @@
 
 import io.netty.util.ThreadDeathWatcher;
 import io.netty.util.concurrent.GlobalEventExecutor;
-
 import org.elasticsearch.client.transport.TransportClient;
 import org.elasticsearch.common.SuppressForbidden;
 import org.elasticsearch.common.network.NetworkModule;
@@ -35,7 +34,7 @@
 
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
+import java.util.List;
 import java.util.concurrent.TimeUnit;
 
 /**
@@ -87,13 +86,7 @@ private static void setSystemPropertyIfUnset(final String key, final String valu
     }
 
     private static final Collection<Class<? extends Plugin>> PRE_INSTALLED_PLUGINS =
-        Collections.unmodifiableList(
-            Arrays.asList(
-                Netty4Plugin.class,
-                ReindexPlugin.class,
-                PercolatorPlugin.class,
-                MustachePlugin.class,
-                ParentJoinPlugin.class));
+            List.of(Netty4Plugin.class, ReindexPlugin.class, PercolatorPlugin.class, MustachePlugin.class, ParentJoinPlugin.class);
 
     /**
      * Creates a new transport client with pre-installed plugins.

libs/x-content/src/test/java/org/elasticsearch/common/xcontent/ConstructingObjectParserTests.java

@@ -29,10 +29,8 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.util.Arrays;
 import java.util.List;
 
-import static java.util.Collections.unmodifiableList;
 import static org.elasticsearch.common.xcontent.ConstructingObjectParser.constructorArg;
 import static org.elasticsearch.common.xcontent.ConstructingObjectParser.optionalConstructorArg;
 import static org.hamcrest.Matchers.anyOf;
@@ -378,8 +376,8 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         public static final ConstructingObjectParser<HasCtorArguments, Void> PARSER_VEGETABLE_OPTIONAL = buildParser(true, false);
         public static final ConstructingObjectParser<HasCtorArguments, Void> PARSER_ALL_OPTIONAL = buildParser(false, false);
 
-        public static final List<ConstructingObjectParser<HasCtorArguments, Void>> ALL_PARSERS = unmodifiableList(
-                Arrays.asList(PARSER, PARSER_VEGETABLE_OPTIONAL, PARSER_ALL_OPTIONAL));
+        public static final List<ConstructingObjectParser<HasCtorArguments, Void>> ALL_PARSERS =
+                List.of(PARSER, PARSER_VEGETABLE_OPTIONAL, PARSER_ALL_OPTIONAL);
 
         public static final ConstructingObjectParser<HasCtorArguments, Integer> PARSER_INT_CONTEXT = buildContextParser();