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chia7712 merged 2 commits into from
Mar 30, 2026
Merged

MINOR: Replace Collections factory methods with Java 11+ equivalents in group-coordinator and part of clients #21876

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MINOR: Replace Collections factory methods with Java 11+ equivalents …
see-quick Mar 23, 2026
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see-quick Mar 27, 2026
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12 changes: 6 additions & 6 deletions clients/src/main/java/org/apache/kafka/common/config/AbstractConfig.java
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Original file line number Diff line number Diff line change
Expand Up @@ -133,7 +133,7 @@ public AbstractConfig(ConfigDef definition, Map<?, ?> originals, Map<String, ?>
* @param originals the configuration properties plus any optional config provider properties; may not be null
*/
public AbstractConfig(ConfigDef definition, Map<?, ?> originals) {
this(definition, originals, Collections.emptyMap(), true);
this(definition, originals, Map.of(), true);
}

/**
Expand All @@ -146,7 +146,7 @@ public AbstractConfig(ConfigDef definition, Map<?, ?> originals) {
* @param doLog whether the configurations should be logged
*/
public AbstractConfig(ConfigDef definition, Map<?, ?> originals, boolean doLog) {
this(definition, originals, Collections.emptyMap(), doLog);
this(definition, originals, Map.of(), doLog);
}

/**
Expand All @@ -168,7 +168,7 @@ protected Map<String, Object> preProcessParsedConfig(Map<String, Object> parsedV
* @return a map of updates that should be applied to the configuration (will be validated to prevent bad updates)
*/
protected Map<String, Object> postProcessParsedConfig(Map<String, Object> parsedValues) {
return Collections.emptyMap();
return Map.of();
}

protected Object get(String key) {
Expand Down Expand Up @@ -430,7 +430,7 @@ private <T> T getConfiguredInstance(Object klass, Class<T> t, Map<String, Object
* @return A configured instance of the class
*/
public <T> T getConfiguredInstance(String key, Class<T> t) {
return getConfiguredInstance(key, t, Collections.emptyMap());
return getConfiguredInstance(key, t, Map.of());
}

/**
Expand Down Expand Up @@ -458,7 +458,7 @@ public <T> T getConfiguredInstance(String key, Class<T> t, Map<String, Object> c
* @return The list of configured instances
*/
public <T> List<T> getConfiguredInstances(String key, Class<T> t) {
return getConfiguredInstances(key, t, Collections.emptyMap());
return getConfiguredInstances(key, t, Map.of());
}

/**
Expand Down Expand Up @@ -606,7 +606,7 @@ private Map<String, ConfigProvider> instantiateConfigProviders(
final String configProviders = indirectConfigs.get(CONFIG_PROVIDERS_CONFIG);

if (configProviders == null || configProviders.isEmpty()) {
return Collections.emptyMap();
return Map.of();
}

Map<String, String> providerMap = new HashMap<>();
Expand Down
26 changes: 13 additions & 13 deletions clients/src/main/java/org/apache/kafka/common/config/ConfigDef.java
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Expand Up @@ -218,7 +218,7 @@ public ConfigDef define(String name, Type type, Object defaultValue, Validator v
*/
public ConfigDef define(String name, Type type, Object defaultValue, Validator validator, Importance importance, String documentation,
String group, int orderInGroup, Width width, String displayName, Recommender recommender) {
return define(name, type, defaultValue, validator, importance, documentation, group, orderInGroup, width, displayName, Collections.emptyList(), recommender);
return define(name, type, defaultValue, validator, importance, documentation, group, orderInGroup, width, displayName, List.of(), recommender);
}

/**
Expand All @@ -237,7 +237,7 @@ public ConfigDef define(String name, Type type, Object defaultValue, Validator v
*/
public ConfigDef define(String name, Type type, Object defaultValue, Validator validator, Importance importance, String documentation,
String group, int orderInGroup, Width width, String displayName) {
return define(name, type, defaultValue, validator, importance, documentation, group, orderInGroup, width, displayName, Collections.emptyList());
return define(name, type, defaultValue, validator, importance, documentation, group, orderInGroup, width, displayName, List.of());
}

/**
Expand Down Expand Up @@ -295,7 +295,7 @@ public ConfigDef define(String name, Type type, Object defaultValue, Importance
*/
public ConfigDef define(String name, Type type, Object defaultValue, Importance importance, String documentation,
String group, int orderInGroup, Width width, String displayName, Recommender recommender) {
return define(name, type, defaultValue, null, importance, documentation, group, orderInGroup, width, displayName, Collections.emptyList(), recommender);
return define(name, type, defaultValue, null, importance, documentation, group, orderInGroup, width, displayName, List.of(), recommender);
}

/**
Expand All @@ -313,7 +313,7 @@ public ConfigDef define(String name, Type type, Object defaultValue, Importance
*/
public ConfigDef define(String name, Type type, Object defaultValue, Importance importance, String documentation,
String group, int orderInGroup, Width width, String displayName) {
return define(name, type, defaultValue, null, importance, documentation, group, orderInGroup, width, displayName, Collections.emptyList());
return define(name, type, defaultValue, null, importance, documentation, group, orderInGroup, width, displayName, List.of());
}

/**
Expand Down Expand Up @@ -368,7 +368,7 @@ public ConfigDef define(String name, Type type, Importance importance, String do
*/
public ConfigDef define(String name, Type type, Importance importance, String documentation, String group, int orderInGroup,
Width width, String displayName, Recommender recommender) {
return define(name, type, NO_DEFAULT_VALUE, null, importance, documentation, group, orderInGroup, width, displayName, Collections.emptyList(), recommender);
return define(name, type, NO_DEFAULT_VALUE, null, importance, documentation, group, orderInGroup, width, displayName, List.of(), recommender);
}

/**
Expand All @@ -385,7 +385,7 @@ public ConfigDef define(String name, Type type, Importance importance, String do
*/
public ConfigDef define(String name, Type type, Importance importance, String documentation, String group, int orderInGroup,
Width width, String displayName) {
return define(name, type, NO_DEFAULT_VALUE, null, importance, documentation, group, orderInGroup, width, displayName, Collections.emptyList());
return define(name, type, NO_DEFAULT_VALUE, null, importance, documentation, group, orderInGroup, width, displayName, List.of());
}

/**
Expand Down Expand Up @@ -427,7 +427,7 @@ public ConfigDef define(String name, Type type, Object defaultValue, Importance
*/
public ConfigDef define(String name, Type type, Object defaultValue, Importance importance, String documentation, String alternativeString) {
return define(name, type, defaultValue, null, importance, documentation, null, -1, Width.NONE,
name, Collections.emptyList(), null, alternativeString);
name, List.of(), null, alternativeString);
}

/**
Expand All @@ -452,7 +452,7 @@ public ConfigDef define(String name, Type type, Importance importance, String do
* @return This ConfigDef so you can chain calls
*/
public ConfigDef defineInternal(final String name, final Type type, final Object defaultValue, final Importance importance) {
return define(new ConfigKey(name, type, defaultValue, null, importance, "", "", -1, Width.NONE, name, Collections.emptyList(), null, true, null));
return define(new ConfigKey(name, type, defaultValue, null, importance, "", "", -1, Width.NONE, name, List.of(), null, true, null));
}

/**
Expand All @@ -467,7 +467,7 @@ public ConfigDef defineInternal(final String name, final Type type, final Object
* @return This ConfigDef so you can chain calls
*/
public ConfigDef defineInternal(final String name, final Type type, final Object defaultValue, final Validator validator, final Importance importance, final String documentation) {
return define(new ConfigKey(name, type, defaultValue, validator, importance, documentation, "", -1, Width.NONE, name, Collections.emptyList(), null, true, null));
return define(new ConfigKey(name, type, defaultValue, validator, importance, documentation, "", -1, Width.NONE, name, List.of(), null, true, null));
}

/**
Expand Down Expand Up @@ -768,7 +768,7 @@ else if (value instanceof String)
return value;
else if (value instanceof String)
if (trimmed.isEmpty())
return Collections.emptyList();
return List.of();
else
return Arrays.asList(COMMA_WITH_WHITESPACE.split(trimmed, -1));
else
Expand Down Expand Up @@ -1445,7 +1445,7 @@ static String niceTimeUnits(long millis) {
}

public String toHtmlTable() {
return toHtmlTable(Collections.emptyMap());
return toHtmlTable(Map.of());
}

private void addHeader(StringBuilder builder, String headerName) {
Expand Down Expand Up @@ -1700,7 +1700,7 @@ public boolean visible(String name, Map<String, Object> parsedConfig) {
}

public String toHtml() {
return toHtml(Collections.emptyMap());
return toHtml(Map.of());
}

/**
Expand All @@ -1709,7 +1709,7 @@ public String toHtml() {
* @param idGenerator A function for computing the HTML id attribute in the generated HTML from a given config name.
*/
public String toHtml(int headerDepth, Function<String, String> idGenerator) {
return toHtml(headerDepth, idGenerator, Collections.emptyMap());
return toHtml(headerDepth, idGenerator, Map.of());
}

/**
Expand Down
5 changes: 2 additions & 3 deletions clients/src/main/java/org/apache/kafka/common/config/internals/BrokerSecurityConfigs.java
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Expand Up @@ -25,7 +25,6 @@
import org.apache.kafka.common.security.authenticator.DefaultKafkaPrincipalBuilder;
import org.apache.kafka.common.utils.Utils;

import java.util.Collections;
import java.util.List;

import static org.apache.kafka.common.config.ConfigDef.Importance.LOW;
Expand Down Expand Up @@ -61,7 +60,7 @@ public class BrokerSecurityConfigs {
" configuration.";

public static final String SASL_KERBEROS_PRINCIPAL_TO_LOCAL_RULES_CONFIG = "sasl.kerberos.principal.to.local.rules";
public static final List<String> DEFAULT_SASL_KERBEROS_PRINCIPAL_TO_LOCAL_RULES = Collections.singletonList(DEFAULT_SSL_PRINCIPAL_MAPPING_RULES);
public static final List<String> DEFAULT_SASL_KERBEROS_PRINCIPAL_TO_LOCAL_RULES = List.of(DEFAULT_SSL_PRINCIPAL_MAPPING_RULES);
public static final String SASL_KERBEROS_PRINCIPAL_TO_LOCAL_RULES_DOC = "A list of rules for mapping from principal " +
"names to short names (typically operating system usernames). The rules are evaluated in order and the " +
"first rule that matches a principal name is used to map it to a short name. Any later rules in the list are " +
Expand Down Expand Up @@ -95,7 +94,7 @@ public class BrokerSecurityConfigs {
+ "</ul>";

public static final String SASL_ENABLED_MECHANISMS_CONFIG = "sasl.enabled.mechanisms";
public static final List<String> DEFAULT_SASL_ENABLED_MECHANISMS = Collections.singletonList(SaslConfigs.GSSAPI_MECHANISM);
public static final List<String> DEFAULT_SASL_ENABLED_MECHANISMS = List.of(SaslConfigs.GSSAPI_MECHANISM);
public static final String SASL_ENABLED_MECHANISMS_DOC = "The list of SASL mechanisms enabled in the Kafka server. "
+ "The list may contain any mechanism for which a security provider is available. "
+ "Only GSSAPI is enabled by default.";
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/config/provider/DirectoryConfigProvider.java
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Expand Up @@ -32,7 +32,6 @@
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static java.util.Collections.emptyMap;

/**
* An implementation of {@link ConfigProvider} based on a directory of files.
Expand Down Expand Up @@ -87,7 +86,7 @@ private ConfigData get(String path, Predicate<Path> fileFilter) {
throw new IllegalStateException("The provider has not been configured yet.");
}

Map<String, String> map = emptyMap();
Map<String, String> map = Map.of();

if (path != null && !path.isEmpty()) {
Path dir = allowedPaths.parseUntrustedPath(path);
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/errors/TopicAuthorizationException.java
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Expand Up @@ -16,7 +16,6 @@
*/
package org.apache.kafka.common.errors;

import java.util.Collections;
import java.util.Set;

public class TopicAuthorizationException extends AuthorizationException {
Expand All @@ -32,7 +31,7 @@ public TopicAuthorizationException(Set<String> unauthorizedTopics) {
}

public TopicAuthorizationException(String message) {
this(message, Collections.emptySet());
this(message, Set.of());
}

/**
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/AbstractResponse.java
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Expand Up @@ -26,7 +26,6 @@

import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumMap;
import java.util.Map;
import java.util.stream.Collectors;
Expand Down Expand Up @@ -65,7 +64,7 @@ final ByteBufferAccessor serialize(short version) {
public abstract Map<Errors, Integer> errorCounts();

protected static Map<Errors, Integer> errorCounts(Errors error) {
return Collections.singletonMap(error, 1);
return Map.of(error, 1);
}

protected static Map<Errors, Integer> errorCounts(Stream<Errors> errors) {
Expand Down
5 changes: 2 additions & 3 deletions clients/src/main/java/org/apache/kafka/common/requests/AddRaftVoterResponse.java
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Expand Up @@ -22,7 +22,6 @@
import org.apache.kafka.common.protocol.Errors;
import org.apache.kafka.common.protocol.Readable;

import java.util.Collections;
import java.util.Map;

public class AddRaftVoterResponse extends AbstractResponse {
Expand Down Expand Up @@ -51,9 +50,9 @@ public void maybeSetThrottleTimeMs(int throttleTimeMs) {
@Override
public Map<Errors, Integer> errorCounts() {
if (data.errorCode() != Errors.NONE.code()) {
return Collections.singletonMap(Errors.forCode(data.errorCode()), 1);
return Map.of(Errors.forCode(data.errorCode()), 1);
} else {
return Collections.emptyMap();
return Map.of();
}
}

Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/AllocateProducerIdsResponse.java
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Expand Up @@ -22,7 +22,6 @@
import org.apache.kafka.common.protocol.Errors;
import org.apache.kafka.common.protocol.Readable;

import java.util.Collections;
import java.util.Map;

public class AllocateProducerIdsResponse extends AbstractResponse {
Expand All @@ -47,7 +46,7 @@ public AllocateProducerIdsResponseData data() {
*/
@Override
public Map<Errors, Integer> errorCounts() {
return Collections.singletonMap(Errors.forCode(data.errorCode()), 1);
return Map.of(Errors.forCode(data.errorCode()), 1);
}

@Override
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/AlterPartitionRequest.java
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Expand Up @@ -25,7 +25,6 @@
import org.apache.kafka.common.protocol.Readable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

Expand Down Expand Up @@ -90,7 +89,7 @@ public AlterPartitionRequest build(short version) {
newIsr.add(brokerState.brokerId())
);
partitionData.setNewIsr(newIsr);
partitionData.setNewIsrWithEpochs(Collections.emptyList());
partitionData.setNewIsrWithEpochs(List.of());
}
})
);
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/AssignReplicasToDirsResponse.java
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Expand Up @@ -21,7 +21,6 @@
import org.apache.kafka.common.protocol.Errors;
import org.apache.kafka.common.protocol.Readable;

import java.util.Collections;
import java.util.Map;

public class AssignReplicasToDirsResponse extends AbstractResponse {
Expand All @@ -40,7 +39,7 @@ public AssignReplicasToDirsResponseData data() {

@Override
public Map<Errors, Integer> errorCounts() {
return Collections.singletonMap(Errors.forCode(data.errorCode()), 1);
return Map.of(Errors.forCode(data.errorCode()), 1);
}

@Override
Expand Down
7 changes: 4 additions & 3 deletions clients/src/main/java/org/apache/kafka/common/requests/BeginQuorumEpochRequest.java
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Expand Up @@ -23,7 +23,8 @@
import org.apache.kafka.common.protocol.Errors;
import org.apache.kafka.common.protocol.Readable;

import java.util.Collections;
import java.util.List;


public class BeginQuorumEpochRequest extends AbstractRequest {
public static class Builder extends AbstractRequest.Builder<BeginQuorumEpochRequest> {
Expand Down Expand Up @@ -75,10 +76,10 @@ public static BeginQuorumEpochRequestData singletonRequest(
) {
return new BeginQuorumEpochRequestData()
.setClusterId(clusterId)
.setTopics(Collections.singletonList(
.setTopics(List.of(
new BeginQuorumEpochRequestData.TopicData()
.setTopicName(topicPartition.topic())
.setPartitions(Collections.singletonList(
.setPartitions(List.of(
new BeginQuorumEpochRequestData.PartitionData()
.setPartitionIndex(topicPartition.partition())
.setLeaderEpoch(leaderEpoch)
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/ConsumerGroupHeartbeatResponse.java
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Expand Up @@ -23,7 +23,6 @@
import org.apache.kafka.common.protocol.Readable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
Expand Down Expand Up @@ -59,7 +58,7 @@ public ConsumerGroupHeartbeatResponseData data() {

@Override
public Map<Errors, Integer> errorCounts() {
return Collections.singletonMap(Errors.forCode(data.errorCode()), 1);
return Map.of(Errors.forCode(data.errorCode()), 1);
}

@Override
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/ControllerRegistrationResponse.java
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Expand Up @@ -22,7 +22,6 @@
import org.apache.kafka.common.protocol.Errors;
import org.apache.kafka.common.protocol.Readable;

import java.util.Collections;
import java.util.Map;

public class ControllerRegistrationResponse extends AbstractResponse {
Expand Down Expand Up @@ -50,7 +49,7 @@ public void maybeSetThrottleTimeMs(int throttleTimeMs) {

@Override
public Map<Errors, Integer> errorCounts() {
return Collections.singletonMap(Errors.forCode(data.errorCode()), 1);
return Map.of(Errors.forCode(data.errorCode()), 1);
}

public static ControllerRegistrationResponse parse(Readable readable, short version) {
Expand Down
3 changes: 1 addition & 2 deletions clients/src/main/java/org/apache/kafka/common/requests/DeleteTopicsRequest.java
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Expand Up @@ -25,7 +25,6 @@
import org.apache.kafka.common.protocol.Readable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

Expand Down Expand Up @@ -104,7 +103,7 @@ public int numberOfTopics() {
public List<Uuid> topicIds() {
if (version() >= 6)
return data.topics().stream().map(DeleteTopicState::topicId).collect(Collectors.toList());
return Collections.emptyList();
return List.of();
}

public List<DeleteTopicState> topics() {
Expand Down
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