Reenable Checkstyle's unused import rule

buildSrc/src/main/resources/checkstyle.xml

@@ -26,13 +26,9 @@
     </module>
 
     <module name="AvoidStarImport" />
-    <!-- Doesn't pass but we could make it pass pretty quick.
-    <module name="UnusedImports">
-      The next property is optional. If we remove it then imports that are
-      only referenced by Javadoc cause the check to fail.
-      <property name="processJavadoc" value="true" />
-    </module>
-    -->
+
+    <!-- Unused imports are forbidden -->
+    <module name="UnusedImports" />
 
     <!-- Non-inner classes must be in files that match their names. -->
     <module name="OuterTypeFilename" />

client/rest/src/test/java/org/elasticsearch/client/RestClientMultipleHostsIntegTests.java

@@ -33,14 +33,12 @@
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
-import static java.util.Collections.singletonList;
 import static org.elasticsearch.client.RestClientTestUtil.getAllStatusCodes;
 import static org.elasticsearch.client.RestClientTestUtil.randomErrorNoRetryStatusCode;
 import static org.elasticsearch.client.RestClientTestUtil.randomOkStatusCode;

client/rest/src/test/java/org/elasticsearch/client/RestClientMultipleHostsTests.java

@@ -53,14 +53,12 @@
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 
-import static java.util.Collections.singletonList;
 import static org.elasticsearch.client.RestClientTestUtil.randomErrorNoRetryStatusCode;
 import static org.elasticsearch.client.RestClientTestUtil.randomErrorRetryStatusCode;
 import static org.elasticsearch.client.RestClientTestUtil.randomHttpMethod;
 import static org.elasticsearch.client.RestClientTestUtil.randomOkStatusCode;
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.instanceOf;
-import static org.hamcrest.Matchers.hasItem;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;

client/rest/src/test/java/org/elasticsearch/client/documentation/RestClientDocumentation.java

@@ -36,7 +36,6 @@
 import org.apache.http.ssl.SSLContextBuilder;
 import org.apache.http.ssl.SSLContexts;
 import org.apache.http.util.EntityUtils;
-import org.elasticsearch.client.HttpAsyncResponseConsumerFactory;
 import org.elasticsearch.client.HttpAsyncResponseConsumerFactory.HeapBufferedResponseConsumerFactory;
 import org.elasticsearch.client.Node;
 import org.elasticsearch.client.NodeSelector;

client/sniffer/src/main/java/org/elasticsearch/client/sniff/ElasticsearchNodesSniffer.java

@@ -36,10 +36,8 @@
 import java.io.InputStream;
 import java.net.URI;
 import java.util.ArrayList;
-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.concurrent.TimeUnit;

client/sniffer/src/main/java/org/elasticsearch/client/sniff/SniffOnFailureListener.java

@@ -19,7 +19,6 @@
 
 package org.elasticsearch.client.sniff;
 
-import org.apache.http.HttpHost;
 import org.elasticsearch.client.Node;
 import org.elasticsearch.client.RestClient;
 

plugins/repository-azure/src/main/java/org/elasticsearch/repositories/azure/AzureBlobContainer.java

@@ -32,7 +32,6 @@
 import java.io.InputStream;
 import java.net.HttpURLConnection;
 import java.net.URISyntaxException;
-import java.nio.file.FileAlreadyExistsException;
 import java.nio.file.NoSuchFileException;
 import java.util.Map;
 

server/src/main/java/org/elasticsearch/action/bulk/TransportShardBulkAction.java

@@ -29,7 +29,6 @@
 import org.elasticsearch.action.index.IndexRequest;
 import org.elasticsearch.action.index.IndexResponse;
 import org.elasticsearch.action.support.ActionFilters;
-import org.elasticsearch.action.support.TransportActions;
 import org.elasticsearch.action.support.replication.ReplicationOperation;
 import org.elasticsearch.action.support.replication.ReplicationResponse.ShardInfo;
 import org.elasticsearch.action.support.replication.TransportReplicationAction;

server/src/main/java/org/elasticsearch/common/CheckedRunnable.java

@@ -19,8 +19,6 @@
 
 package org.elasticsearch.common;
 
-import java.lang.Runnable;
-
 /**
  * A {@link Runnable}-like interface which allows throwing checked exceptions.
  */

server/src/main/java/org/elasticsearch/common/lucene/search/function/FunctionScoreQuery.java

@@ -30,8 +30,6 @@
 import org.apache.lucene.search.ScorerSupplier;
 import org.apache.lucene.search.Weight;
 import org.apache.lucene.util.Bits;
-import org.apache.lucene.search.TopDocsCollector;
-import org.apache.lucene.search.TopScoreDocCollector;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -376,9 +374,9 @@ public float score() throws IOException {
             double factor = computeScore(docId, subQueryScore);
             float finalScore = scoreCombiner.combine(subQueryScore, factor, maxBoost);
             if (finalScore == Float.NEGATIVE_INFINITY || Float.isNaN(finalScore)) {
-                /**
-                 * These scores are invalid for score based {@link TopDocsCollector}s.
-                 * See {@link TopScoreDocCollector} for details.
+                /*
+                  These scores are invalid for score based {@link org.apache.lucene.search.TopDocsCollector}s.
+                  See {@link org.apache.lucene.search.TopScoreDocCollector} for details.
                  */
                 throw new ElasticsearchException("function score query returned an invalid score: " + finalScore + " for doc: " + docId);
             }

server/src/main/java/org/elasticsearch/index/search/MatchQuery.java

@@ -51,7 +51,6 @@
 import org.elasticsearch.common.lucene.search.MultiPhrasePrefixQuery;
 import org.elasticsearch.common.lucene.search.Queries;
 import org.elasticsearch.common.unit.Fuzziness;
-import org.elasticsearch.index.analysis.ShingleTokenFilterFactory;
 import org.elasticsearch.index.mapper.KeywordFieldMapper;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.query.QueryShardContext;
@@ -62,7 +61,7 @@
 import static org.elasticsearch.common.lucene.search.Queries.newLenientFieldQuery;
 import static org.elasticsearch.common.lucene.search.Queries.newUnmappedFieldQuery;
 
-public class MatchQuery {
+public class    MatchQuery {
 
     public enum Type implements Writeable {
         /**
@@ -401,9 +400,9 @@ protected Query createFieldQuery(Analyzer analyzer, BooleanClause.Occur operator
             // query based on the analysis chain.
             try (TokenStream source = analyzer.tokenStream(field, queryText)) {
                 if (source.hasAttribute(DisableGraphAttribute.class)) {
-                    /**
-                     * A {@link TokenFilter} in this {@link TokenStream} disabled the graph analysis to avoid
-                     * paths explosion. See {@link ShingleTokenFilterFactory} for details.
+                    /*
+                      A {@link TokenFilter} in this {@link TokenStream} disabled the graph analysis to avoid
+                      paths explosion. See {@link org.elasticsearch.index.analysis.ShingleTokenFilterFactory} for details.
                      */
                     setEnableGraphQueries(false);
                 }

server/src/main/java/org/elasticsearch/index/shard/PrimaryReplicaSyncer.java

@@ -35,7 +35,6 @@
 import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.common.util.concurrent.AbstractRunnable;
 import org.elasticsearch.common.xcontent.XContentBuilder;
-import org.elasticsearch.index.seqno.SeqNoStats;
 import org.elasticsearch.index.seqno.SequenceNumbers;
 import org.elasticsearch.index.translog.Translog;
 import org.elasticsearch.tasks.Task;

server/src/main/java/org/elasticsearch/search/aggregations/bucket/composite/CompositeAggregator.java

@@ -25,7 +25,6 @@
 import org.apache.lucene.search.CollectionTerminatedException;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
-import org.apache.lucene.search.MultiCollector;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.Scorer;
 import org.apache.lucene.search.Weight;
@@ -147,20 +146,20 @@ protected LeafBucketCollector getLeafCollector(LeafReaderContext ctx, LeafBucket
         finishLeaf();
         boolean fillDocIdSet = deferredCollectors != NO_OP_COLLECTOR;
         if (sortedDocsProducer != null) {
-            /**
-             * The producer will visit documents sorted by the leading source of the composite definition
-             * and terminates when the leading source value is guaranteed to be greater than the lowest
-             * composite bucket in the queue.
+            /*
+              The producer will visit documents sorted by the leading source of the composite definition
+              and terminates when the leading source value is guaranteed to be greater than the lowest
+              composite bucket in the queue.
              */
             DocIdSet docIdSet = sortedDocsProducer.processLeaf(context.query(), queue, ctx, fillDocIdSet);
             if (fillDocIdSet) {
                 entries.add(new Entry(ctx, docIdSet));
             }
 
-            /**
-             * We can bypass search entirely for this segment, all the processing has been done in the previous call.
-             * Throwing this exception will terminate the execution of the search for this root aggregation,
-             * see {@link MultiCollector} for more details on how we handle early termination in aggregations.
+            /*
+              We can bypass search entirely for this segment, all the processing has been done in the previous call.
+              Throwing this exception will terminate the execution of the search for this root aggregation,
+              see {@link org.apache.lucene.search.MultiCollector} for more details on how we handle early termination in aggregations.
              */
             throw new CollectionTerminatedException();
         } else {

server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/HighlightPhase.java

@@ -23,7 +23,6 @@
 import org.elasticsearch.common.component.AbstractComponent;
 import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.index.mapper.DocumentMapper;
 import org.elasticsearch.index.mapper.KeywordFieldMapper;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.SourceFieldMapper;

server/src/main/java9/org/elasticsearch/monitor/jvm/JvmPid.java

@@ -19,8 +19,6 @@
 
 package org.elasticsearch.monitor.jvm;
 
-import java.lang.ProcessHandle;
-
 class JvmPid {
 
     static long getPid() {

test/framework/src/main/java/org/elasticsearch/index/replication/ESIndexLevelReplicationTestCase.java

@@ -74,7 +74,6 @@
 import org.elasticsearch.threadpool.ThreadPool;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/saml/SamlAuthenticatorTests.java

@@ -14,7 +14,6 @@
 import org.apache.xml.security.keys.content.X509Data;
 import org.elasticsearch.ElasticsearchSecurityException;
 import org.elasticsearch.common.CheckedConsumer;
-import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.logging.Loggers;

x-pack/qa/ml-native-tests/src/test/java/org/elasticsearch/xpack/ml/integration/DetectionRulesIT.java

@@ -24,7 +24,6 @@
 import org.elasticsearch.xpack.core.ml.job.config.RuleConditionType;
 import org.elasticsearch.xpack.core.ml.job.results.AnomalyRecord;
 import org.junit.After;
-import org.junit.Ignore;
 
 import java.io.IOException;
 import java.util.ArrayList;

x-pack/qa/ml-native-tests/src/test/java/org/elasticsearch/xpack/ml/integration/ScheduledEventsIT.java

@@ -20,7 +20,6 @@
 import org.elasticsearch.xpack.core.ml.job.results.AnomalyRecord;
 import org.elasticsearch.xpack.core.ml.job.results.Bucket;
 import org.junit.After;
-import org.junit.Ignore;
 
 import java.io.IOException;
 import java.time.Instant;

x-pack/qa/security-example-spi-extension/src/test/java/org/elasticsearch/example/role/CustomRolesProviderIT.java

@@ -14,7 +14,6 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.example.realm.CustomRealm;
 import org.elasticsearch.plugins.Plugin;
-import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xpack.core.XPackClientPlugin;
 import org.elasticsearch.xpack.core.security.authc.support.UsernamePasswordToken;
 import org.elasticsearch.xpack.core.security.client.SecurityClient;

x-pack/qa/smoke-test-plugins-ssl/src/test/java/org/elasticsearch/smoketest/SmokeTestMonitoringWithSecurityIT.java

@@ -11,7 +11,6 @@
 import org.elasticsearch.common.network.NetworkModule;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.plugins.Plugin;
-import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.xpack.core.XPackPlugin;
 import org.elasticsearch.xpack.core.action.XPackUsageRequestBuilder;
 import org.elasticsearch.xpack.core.action.XPackUsageResponse;
@@ -95,7 +94,7 @@ private boolean getMonitoringUsageExportersDefined() throws Exception {
     public void testHTTPExporterWithSSL() throws Exception {
         // Ensures that the exporter is actually on
         assertBusy(() -> assertThat("[_http] exporter is not defined", getMonitoringUsageExportersDefined(), is(true)));
-        
+
         // Checks that the monitoring index templates have been installed
         assertBusy(() -> {
             GetIndexTemplatesResponse response = client().admin().indices().prepareGetTemplates(MONITORING_PATTERN).get();