Use Java 11 collections conveniences everywhere (#41399)

This commit replaces all applicable uses with Java 11 collections
convenience methods.

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

@@ -27,12 +27,14 @@
 import org.elasticsearch.common.xcontent.XContentParserUtils;
 
 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.Map;
 import java.util.Objects;
-import java.util.Set;
+import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import static org.elasticsearch.common.xcontent.ConstructingObjectParser.constructorArg;
 import static org.elasticsearch.common.xcontent.ConstructingObjectParser.optionalConstructorArg;
@@ -42,26 +44,27 @@
  * Returns a List of {@link User} objects
  */
 public class GetUsersResponse {
-    private final Set<User> users;
-    private final Set<User> enabledUsers;
 
-    public GetUsersResponse(Set<User> users, Set<User> enabledUsers) {
-        this.users = Collections.unmodifiableSet(users);
-        this.enabledUsers = Collections.unmodifiableSet(enabledUsers);
+    private final Map<String, User> users;
+    private final Map<String, User> enabledUsers;
+
+    GetUsersResponse(final Map<String, User> users, final Map<String, User> enabledUsers) {
+        this.users = Map.copyOf(users);
+        this.enabledUsers = Map.copyOf(enabledUsers);
     }
 
-    public Set<User> getUsers() {
-        return users;
+    public List<User> getUsers() {
+        return List.copyOf(users.values());
     }
 
-    public Set<User> getEnabledUsers() {
-        return enabledUsers;
+    public List<User> getEnabledUsers() {
+        return List.copyOf(enabledUsers.values());
     }
 
     public static GetUsersResponse fromXContent(XContentParser parser) throws IOException {
         XContentParserUtils.ensureExpectedToken(Token.START_OBJECT, parser.nextToken(), parser::getTokenLocation);
-        final Set<User> users = new HashSet<>();
-        final Set<User> enabledUsers = new HashSet<>();
+        final List<User> users = new ArrayList<>();
+        final List<User> enabledUsers = new ArrayList<>();
         Token token;
         while ((token = parser.nextToken()) != Token.END_OBJECT) {
             XContentParserUtils.ensureExpectedToken(Token.FIELD_NAME, token, parser::getTokenLocation);
@@ -71,7 +74,11 @@ public static GetUsersResponse fromXContent(XContentParser parser) throws IOExce
                 enabledUsers.add(parsedUser.user);
             }
         }
-        return new GetUsersResponse(users, enabledUsers);
+        return new GetUsersResponse(toMap(users), toMap(enabledUsers));
+    }
+
+    static Map<String, User> toMap(final Collection<User> users) {
+        return users.stream().collect(Collectors.toUnmodifiableMap(User::getUsername, Function.identity()));
     }
 
     @Override
@@ -99,7 +106,7 @@ public int hashCode() {
         (constructorObjects) -> {
             int i = 0;
             final String username = (String) constructorObjects[i++];
-            final Collection<String> roles = (Collection<String>) constructorObjects[i++];
+            final List<String> roles = (List<String>) constructorObjects[i++];
             final Map<String, Object> metadata = (Map<String, Object>) constructorObjects[i++];
             final Boolean enabled = (Boolean) constructorObjects[i++];
             final String fullName = (String) constructorObjects[i++];
@@ -120,13 +127,13 @@ protected static final class ParsedUser {
         protected User user;
         protected boolean enabled;
 
-        public ParsedUser(String username, Collection<String> roles, Map<String, Object> metadata, Boolean enabled,
+        public ParsedUser(String username, List<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");
+            List<String> checkedRoles =
+                    List.copyOf(Objects.requireNonNull(roles, "`roles` is required, cannot be null. Pass an empty list 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

@@ -22,12 +22,10 @@
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
 
-import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.Set;
 
 /**
  * A user to be utilized with security APIs.
@@ -36,7 +34,7 @@
 public final class User {
 
     private final String username;
-    private final Set<String> roles;
+    private final List<String> roles;
     private final Map<String, Object> metadata;
     @Nullable private final String fullName;
     @Nullable private final String email;
@@ -50,13 +48,12 @@ public final class User {
      * @param fullName the full name of the user that may be used for display purposes
      * @param email the email address of the user
      */
-    public User(String username, Collection<String> roles, Map<String, Object> metadata, @Nullable String fullName,
+    public User(String username, List<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 = List.copyOf(Objects.requireNonNull(roles, "`roles` is required, cannot be null. Pass an empty list 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;
     }
@@ -67,7 +64,7 @@ public User(String username, Collection<String> roles, Map<String, Object> metad
      * @param username the username, also known as the principal, unique for in the scope of a realm
      * @param roles the roles that this user is assigned
      */
-    public User(String username, Collection<String> roles) {
+    public User(String username, List<String> roles) {
         this(username, roles, Collections.emptyMap(), null, null);
     }
 
@@ -84,7 +81,7 @@ public String getUsername() {
      *          identified by their unique names and each represents as
      *          set of permissions. Can never be {@code null}.
      */
-    public Set<String> getRoles() {
+    public List<String> getRoles() {
         return this.roles;
     }
 

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

@@ -31,9 +31,8 @@
 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;
 
 import static org.elasticsearch.common.xcontent.ConstructingObjectParser.optionalConstructorArg;
 
@@ -44,8 +43,8 @@ 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 +54,15 @@ 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 +71,7 @@ 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;
     }
 
@@ -106,8 +105,8 @@ public static class FieldSecurity implements ToXContentObject {
         @SuppressWarnings("unchecked")
         private static FieldSecurity buildObjectFromParserArgs(Object[] args) {
             return new FieldSecurity(
-                (Collection<String>) args[0],
-                (Collection<String>) args[1]
+                (List<String>) args[0],
+                (List<String>) args[1]
             );
         }
 
@@ -121,31 +120,31 @@ static FieldSecurity parse(XContentParser parser, Void context) throws IOExcepti
         }
 
         // null or singleton '*' means all fields are granted, empty means no fields are granted
-        private final Set<String> grantedFields;
+        private final List<String> grantedFields;
         // null or empty means no fields are denied
-        private final Set<String> deniedFields;
+        private final List<String> deniedFields;
 
         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 : List.copyOf(grantedFields);
             // unspecified denied fields means no restriction
-            this.deniedFields = deniedFields == null ? null : Collections.unmodifiableSet(new HashSet<>(deniedFields));
+            this.deniedFields = deniedFields == null ? null : List.copyOf(deniedFields);
         }
 
         /**
          * The document fields that can be read or queried. Can be null, in this case
          * all the document's fields are granted access to. Can also be empty, in which
          * case no fields are granted access to.
          */
-        public Set<String> getGrantedFields() {
+        public List<String> getGrantedFields() {
             return grantedFields;
         }
 
         /**
          * The document fields that cannot be accessed or queried. Can be null or empty,
          * in which case no fields are denied.
          */
-        public Set<String> getDeniedFields() {
+        public List<String> getDeniedFields() {
             return deniedFields;
         }