java.util.stream.Collectors.groupingBy()方法的使用及代码示例

x33g5p2x  于2022-01-17 转载在 其他  
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本文整理了Java中java.util.stream.Collectors.groupingBy()方法的一些代码示例，展示了Collectors.groupingBy()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Collectors.groupingBy()方法的具体详情如下：
包路径：java.util.stream.Collectors
类名称：Collectors
方法名：groupingBy

Collectors.groupingBy介绍

暂无

代码示例

代码示例来源：origin: neo4j/neo4j

  1. private Stream<Map.Entry<String,List<Element>>> indexByName( Collection<Element> visitedProcedures )
  2. {
  3.   return visitedProcedures.stream().collect( groupingBy( this::getName ) ).entrySet().stream();
  4. }

代码示例来源：origin: google/error-prone

  1. /**
  2.  * Returns a collection of method groups for given list of {@code classMethods}.
  3.  *
  4.  * <p>A <i>method group</i> is a list of methods with the same name.
  5.  *
  6.  * <p>It is assumed that given {@code classMethods} really do belong to the same class. The
  7.  * returned collection does not guarantee any particular group ordering.
  8.  */
  9. private static Collection<List<MethodTree>> getMethodGroups(List<MethodTree> classMethods) {
  10.  return classMethods.stream().collect(groupingBy(MethodTree::getName)).values();
  11. }

代码示例来源：origin: SonarSource/sonarqube

  1. public Helper() {
  2.  InputStream inputStream = Helper.class.getResourceAsStream("/responseClasses.config");
  3.  responseTypes = new BufferedReader(new InputStreamReader(inputStream))
  4.   .lines()
  5.   .map(line -> line.split("\\s+"))
  6.   .collect(Collectors.groupingBy(arr -> arr[0]));
  7. }

代码示例来源：origin: RichardWarburton/java-8-lambdas-exercises

  1. public Map<Artist, Integer> numberOfAlbumsDumb(Stream<Album> albums) {
  2.     // BEGIN NUMBER_OF_ALBUMS_DUMB
  3. Map<Artist, List<Album>> albumsByArtist
  4.   = albums.collect(groupingBy(album -> album.getMainMusician()));
  6. Map<Artist, Integer>  numberOfAlbums = new HashMap<>();
  7. for(Entry<Artist, List<Album>> entry : albumsByArtist.entrySet()) {
  8.   numberOfAlbums.put(entry.getKey(), entry.getValue().size());
  9. }
  10.     // END NUMBER_OF_ALBUMS_DUMB
  11.     return numberOfAlbums;
  12.   }

代码示例来源：origin: goldmansachs/gs-collections

  1. @Benchmark
  2. public Map<Boolean, Set<Integer>> groupBy_2_keys_serial_lazy_jdk()
  3. {
  4.   Map<Boolean, Set<Integer>> multimap = this.integersJDK.stream()
  5.       .collect(Collectors.groupingBy(each -> each % 2 == 0, Collectors.toSet()));
  6.   Verify.assertSize(2, multimap);
  7.   return multimap;
  8. }

代码示例来源：origin: confluentinc/ksql

  1. public static Collection<Double> currentConsumptionRateByQuery() {
  2.  return collectorMap.values()
  3.    .stream()
  4.    .filter(collector -> collector.getGroupId() != null)
  5.    .collect(
  6.      Collectors.groupingBy(
  7.       MetricCollector::getGroupId,
  8.       Collectors.summingDouble(
  9.         m -> m.aggregateStat(ConsumerCollector.CONSUMER_MESSAGES_PER_SEC, false)
  10.       )
  11.     )
  12.    )
  13.    .values();
  14. }

代码示例来源：origin: stackoverflow.com

  1. import java.util.*;
  2. import java.util.stream.*;
  4. class Test {
  5.   public static void main(String[] args) {
  6.     List<String> list = new ArrayList<>();
  8.     list.add("Hello");
  9.     list.add("Hello");
  10.     list.add("World");
  12.     Map<String, Long> counted = list.stream()
  13.       .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
  15.     System.out.println(counted);
  16.   }
  17. }

代码示例来源：origin: apache/flink

  1. @Override
  2.   @Nonnull
  3.   Map<String, String> expected(@Nonnull List<ValueWithTs<Tuple2<String, String>>> updates, long currentTimestamp) {
  4.     return updates.stream()
  5.       .collect(Collectors.groupingBy(u -> u.getValue().f0))
  6.       .entrySet().stream()
  7.       .map(e -> e.getValue().get(e.getValue().size() - 1))
  8.       .filter(u -> !expired(u.getTimestamp(), currentTimestamp))
  9.       .map(ValueWithTs::getValue)
  10.       .collect(Collectors.toMap(u -> u.f0, u -> u.f1));
  11.   }
  12. }

代码示例来源：origin: apache/storm

  1. private Collection<List<ProcessorNode>> parallelismGroups(List<ProcessorNode> processorNodes) {
  2.   return processorNodes.stream().collect(Collectors.groupingBy(Node::getParallelism)).values();
  3. }

代码示例来源：origin: apache/nifi

  1. public Map<QueuePartition, List<FlowFileRecord>> distributeToPartitionsAndGet(final Collection<FlowFileRecord> flowFiles) {
  2.   if (flowFiles == null || flowFiles.isEmpty()) {
  3.     return Collections.emptyMap();
  4.   }
  5.   final Map<QueuePartition, List<FlowFileRecord>> partitionMap;
  6.   partitionReadLock.lock();
  7.   try {
  8.     // Optimize for the most common case (no load balancing) so that we will just call getPartition() for the first FlowFile
  9.     // in the Collection and then put all FlowFiles into that QueuePartition. Is fairly expensive to call stream().collect(#groupingBy).
  10.     if (partitioner.isPartitionStatic()) {
  11.       final QueuePartition partition = getPartition(flowFiles.iterator().next());
  12.       partition.putAll(flowFiles);
  13.       final List<FlowFileRecord> flowFileList = (flowFiles instanceof List) ? (List<FlowFileRecord>) flowFiles : new ArrayList<>(flowFiles);
  14.       partitionMap = Collections.singletonMap(partition, flowFileList);
  15.       logger.debug("Partitioner is static so Partitioned FlowFiles as: {}", partitionMap);
  16.       return partitionMap;
  17.     }
  18.     partitionMap = flowFiles.stream().collect(Collectors.groupingBy(this::getPartition));
  19.     logger.debug("Partitioned FlowFiles as: {}", partitionMap);
  20.     for (final Map.Entry<QueuePartition, List<FlowFileRecord>> entry : partitionMap.entrySet()) {
  21.       final QueuePartition partition = entry.getKey();
  22.       final List<FlowFileRecord> flowFilesForPartition = entry.getValue();
  23.       partition.putAll(flowFilesForPartition);
  24.     }
  25.   } finally {
  26.     partitionReadLock.unlock();
  27.   }
  28.   return partitionMap;
  29. }

代码示例来源：origin: goldmansachs/gs-collections

  1. @Benchmark
  2. public Map<Integer, Set<Integer>> groupBy_100_keys_serial_lazy_jdk()
  3. {
  4.   Map<Integer, Set<Integer>> multimap = this.integersJDK.stream().collect(Collectors.groupingBy(each -> each % 100, Collectors.toSet()));
  5.   Verify.assertSize(100, multimap);
  6.   return multimap;
  7. }

代码示例来源：origin: gocd/gocd

  1. public Collection<CombinedPluginInfo> allPluginInfos(String type) {
  2.   if (isBlank(type)) {
  3.     return builders.values().stream()
  4.         .map((Function<MetadataStore, Collection<? extends PluginInfo>>) MetadataStore::allPluginInfos)
  5.         .flatMap((Function<Collection<? extends PluginInfo>, Stream<? extends PluginInfo>>) Collection::stream)
  6.         .collect(Collectors.groupingBy(pluginID(), toCollection(CombinedPluginInfo::new)))
  7.         .values();
  8.   } else if (builders.containsKey(type)) {
  9.     Collection<PluginInfo> pluginInfosForType = builders.get(type).allPluginInfos();
  10.     return pluginInfosForType.stream()
  11.         .map(CombinedPluginInfo::new).collect(toList());
  12.   } else {
  13.     throw new InvalidPluginTypeException();
  14.   }
  15. }

代码示例来源：origin: Graylog2/graylog2-server

  1. @GET
  2. @RequiresPermissions(RestPermissions.USERS_LIST)
  3. @ApiOperation(value = "List all users", notes = "The permissions assigned to the users are always included.")
  4. public UserList listUsers() {
  5.   final List<User> users = userService.loadAll();
  6.   final Collection<MongoDbSession> sessions = sessionService.loadAll();
  7.   // among all active sessions, find the last recently used for each user
  8.   //noinspection OptionalGetWithoutIsPresent
  9.   final Map<String, Optional<MongoDbSession>> lastSessionForUser = sessions.stream()
  10.       .filter(s -> s.getUsernameAttribute().isPresent())
  11.       .collect(groupingBy(s -> s.getUsernameAttribute().get(),
  12.                 maxBy(Comparator.comparing(MongoDbSession::getLastAccessTime))));
  13.   final List<UserSummary> resultUsers = Lists.newArrayListWithCapacity(users.size() + 1);
  14.   final User adminUser = userService.getAdminUser();
  15.   resultUsers.add(toUserResponse(adminUser, lastSessionForUser.getOrDefault(adminUser.getName(), Optional.empty())));
  16.   for (User user : users) {
  17.     resultUsers.add(toUserResponse(user, lastSessionForUser.getOrDefault(user.getName(), Optional.empty())));
  18.   }
  19.   return UserList.create(resultUsers);
  20. }

代码示例来源：origin: languagetool-org/languagetool

  1. private void updateIgnoredWordDictionary() {
  2.  wordsToBeIgnoredDictionary = wordsToBeIgnored
  3.                  .stream()
  4.                  .collect(Collectors.groupingBy(s -> s.substring(0,1), Collectors.toSet()));
  5.  wordsToBeIgnoredDictionaryIgnoreCase = wordsToBeIgnored
  6.                       .stream()
  7.                       .map(s -> s.toLowerCase())
  8.                       .collect(Collectors.groupingBy(s -> s.substring(0,1), Collectors.toSet()));
  9. }

代码示例来源：origin: neo4j/neo4j

  1. public void forEach( BiConsumer<String,URI> consumer )
  2. {
  3.   entries.stream().collect( Collectors.groupingBy( e -> e.key ) )
  4.       .forEach( ( key, list ) -> list.stream()
  5.           .max( Comparator.comparing( e -> e.precedence ) )
  6.           .ifPresent( e -> consumer.accept( key, e.uri ) ) );
  7. }

代码示例来源：origin: checkstyle/checkstyle

  1. /**
  2.  * Generate the map of third party Checkstyle module names to the set of their fully qualified
  3.  * names.
  4.  * @param loader the class loader used to load Checkstyle package names
  5.  * @return the map of third party Checkstyle module names to the set of their fully qualified
  6.  *      names
  7.  */
  8. private Map<String, Set<String>> generateThirdPartyNameToFullModuleName(ClassLoader loader) {
  9.   Map<String, Set<String>> returnValue;
  10.   try {
  11.     returnValue = ModuleReflectionUtil.getCheckstyleModules(packages, loader).stream()
  12.       .collect(Collectors.groupingBy(Class::getSimpleName,
  13.         Collectors.mapping(Class::getCanonicalName, Collectors.toSet())));
  14.   }
  15.   catch (IOException ignore) {
  16.     returnValue = Collections.emptyMap();
  17.   }
  18.   return returnValue;
  19. }

代码示例来源：origin: SonarSource/sonarqube

  1. private static void ensureNoDuplicateName(Set<CoreExtension> coreExtensions) {
  2.  Map<String, Long> nameCounts = coreExtensions.stream()
  3.   .map(CoreExtension::getName)
  4.   .collect(Collectors.groupingBy(t -> t, Collectors.counting()));
  5.  Set<String> duplicatedNames = nameCounts.entrySet().stream()
  6.   .filter(t -> t.getValue() > 1)
  7.   .map(Map.Entry::getKey)
  8.   .collect(MoreCollectors.toSet());
  9.  checkState(duplicatedNames.isEmpty(),
  10.   "Multiple core extensions declare the following names: %s",
  11.   duplicatedNames.stream().sorted().collect(Collectors.joining(", ")));
  12. }

代码示例来源：origin: neo4j/neo4j

  1. private Map<AdminCommandSection,List<AdminCommand.Provider>> groupProvidersBySection()
  2.   {
  3.     List<AdminCommand.Provider> providers = new ArrayList<>();
  4.     commands.getAllProviders().forEach( providers::add );
  5.     return providers.stream().collect( Collectors.groupingBy( AdminCommand.Provider::commandSection ) );
  6.   }
  7. }

代码示例来源：origin: apache/nifi

  1. /**
  2.  * Set input or output DataSet ids for a NiFiFlowPath.
  3.  * The updated ids only containing active ids.
  4.  * @return True if there is any changed IO reference (create, update, delete).
  5.  */
  6. private boolean setChangedIOIds(NiFiFlowPath path, AtlasEntity pathEntity, boolean isInput) {
  7.   Set<AtlasObjectId> ids = isInput ? path.getInputs() : path.getOutputs();
  8.   String targetAttribute = isInput ? ATTR_INPUTS : ATTR_OUTPUTS;
  9.   final Map<EntityChangeType, List<AtlasObjectId>> changedIOIds
  10.       = ids.stream().collect(Collectors.groupingBy(this::getFlowPathIOChangeType));
  11.   // Remove DELETED references.
  12.   final Set<AtlasObjectId> remainingFlowPathIOIds = toRemainingFlowPathIOIds(changedIOIds);
  13.   // If references are changed, update it.
  14.   if (path.isDataSetReferenceChanged(remainingFlowPathIOIds, isInput)) {
  15.     pathEntity.setAttribute(targetAttribute, remainingFlowPathIOIds);
  16.     return true;
  17.   }
  18.   return false;
  19. }

代码示例来源：origin: Graylog2/graylog2-server

  1. @Override
  2. public Map<String, List<StreamRule>> loadForStreamIds(Collection<String> streamIds) {
  3.   final List<ObjectId> objectIds = streamIds.stream()
  4.     .map(ObjectId::new)
  5.     .collect(Collectors.toList());
  6.   final List<DBObject> respStreamRules = query(StreamRuleImpl.class,
  7.     new BasicDBObject(StreamRuleImpl.FIELD_STREAM_ID, new BasicDBObject("$in", objectIds))
  8.   );
  9.   return respStreamRules.stream()
  10.     .map(this::toStreamRule)
  11.     .collect(Collectors.groupingBy(StreamRule::getStreamId));
  12. }

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