{
  "apiKey": 43,
  "type": "request",
  "name": "ElectLeadersRequest",
  "validVersions": "0-1",
  "fields": [
    { "name": "ElectionType", "type": "int8", "versions": "1+",
      "about": "Type of elections to conduct for the partition. A value of '0' elects the preferred replica. A value of '1' elects the first live replica if there are no in-sync replica." },
    { "name": "TopicPartitions", "type": "[]TopicPartitions", "versions": "0+", "nullableVersions": "0+",
      "about": "The topic partitions to elect leaders.",
      "fields": [
        { "name": "Topic", "type": "string", "versions": "0+",
          "about": "The name of a topic." },
        { "name": "PartitionId", "type": "[]int32", "versions": "0+",
          "about": "The partitions of this topic whose leader should be elected." }
      ]
    },
    { "name": "TimeoutMs", "type": "int32", "versions": "0+", "default": "60000",
      "about": "The time in ms to wait for the election to complete." }
  ]
}

{
  "apiKey": 43,
  "type": "response",
  "name": "ElectLeadersResponse",
  "validVersions": "0-1",
  "fields": [
    { "name": "ThrottleTimeMs", "type": "int32", "versions": "0+",
      "about": "The duration in milliseconds for which the request was throttled due to a quota violation, or zero if the request did not violate any quota." },
    { "name": "ErrorCode", "type": "int16", "versions": "1+", "ignorable": false,
      "about": "The top level response error code." },
    { "name": "ReplicaElectionResults", "type": "[]ReplicaElectionResult", "versions": "0+",
      "about": "The election results, or an empty array if the requester did not have permission and the request asks for all partitions.", "fields": [
      { "name": "Topic", "type": "string", "versions": "0+", "entityType": "topicName",
        "about": "The topic name" },
      { "name": "PartitionResult", "type": "[]PartitionResult", "versions": "0+",
        "about": "The results for each partition", "fields": [
        { "name": "PartitionId", "type": "int32", "versions": "0+",
          "about": "The partition id" },
        { "name": "ErrorCode", "type": "int16", "versions": "0+",
          "about": "The result error, or zero if there was no error."},
        { "name": "ErrorMessage", "type": "string", "versions": "0+", "nullableVersions": "0+",
          "about": "The result message, or null if there was no error."}
      ]}
    ]}
  ]
}

package org.apache.kafka.clients.admin;

public abstract class AdminClient ... {
    ...

    /**
     * ...
     * @deprecated Since 2.4.0. Use {@link #electLeaders}.
     */
    @Deprecated
    public abstract ElectPreferredLeadersResult electPreferredLeaders(Collection<TopicPartition> partitions,
                                                                      ElectPreferredLeadersOptions options);


    /**
     * ...
     *
     * @param electionType            The type of election.
     * @param partitions              The partitions for which to conduct elections.
     * @param options                 The options to use when electing the leaders.
     * @return                        The ElectLeadersResult.
     */
    public abstract ElectLeadersResult electLeaders(
            ElectionType electionType,
            Set<TopicPartition> partitions,
            ElectLeadersOptions options);
}

final public ElectLeadersResult {
    ...

    public KafkaFuture<Map<TopicPartition, Optional<Throwable>>> partitions() {
        ...
    }

    public KafkFuture<Void> all() {
        ...
    }
}

package org.apache.kafka.common;

public enum ElectionType {
    PREFERRED((byte) 0), UNCLEAN((byte) 1);

    public final byte value;

    ElectionType(byte value) {
        this.value = value;
    }
}

$ bin/kafka-leader-election.sh --help
This tool attempts to elect a new leader for a set of topic partitions. The type of elections supported are preferred replicas and unclean replica.
Option                                  Description
------                                  -----------

--admin.config <String: config file>    Admin client config properties file to pass to the admin
                                          client when --bootstrap-server is given.
--all-topic-partitions                  Perform election on all of the topic partitions. Not allowed if
                                          --topic, --partition or --path-to-json-file is specified.
--bootstrap-server <String: host:port>  A host name and port for the broker to
                                          connect to, in the form host:port.
                                          Multiple comma-separated URLs can be
                                          given. REQUIRED unless --zookeeper
                                          is given.
--election-type <String: election>      Type of election to attempt. Possible values are "preferred"
                                          for preferred election or "unclean" for unclean election.
                                          REQUIRED.
--topic <String: topic>                 Name of topic for which to perform an election.
                                          REQUIRED if --partition is specified. Not allowed
                                          if --path-to-json-file or --all-topic-partitions is specified.
--partition <Integer: partition id>     Partition id for which to perform an election.
                                          REQUIRED if --topic is specified. Not allowed if
                                          --path-to-json-file or --all-topic-partitions is specified.         
--help                                  Print usage information.
--path-to-json-file <String: list of    The JSON file with the list of
  partitions for which replica            partitions for which leader election
  leader election needs to be             should be done. Supported elections
  triggered>                              are 0 for preferred and 1 for unclean.
                                          If an election is not specified,
                                          preferred is the default. This is an
                                          example format.
                                        {"partitions":
                                                [{"topic": "foo", "partition": 1},
                                                 {"topic": "foobar", "partition": 2}]
                                        }
                                          Not allowed if --all-topic-partitions, --topic or --partition
                                          flags are specified.

uncleanElectionFromAdminClient || logConfigs(partition.topic).uncleanLeaderElectionEnable.booleanValue()