public synchronized Map<Subtopology, TopicsInfo> subtopologyToTopicsInfo() {
        final Map<Subtopology, TopicsInfo> topicGroups = new LinkedHashMap<>();

        if (nodeGroups == null) {
            nodeGroups = makeNodeGroups();
        }

        for (final Map.Entry<Integer, Set<String>> entry : nodeGroups.entrySet()) {
            final Set<String> sinkTopics = new HashSet<>();
            final Set<String> sourceTopics = new HashSet<>();
            final Map<String, InternalTopicConfig> repartitionTopics = new HashMap<>();
            final Map<String, InternalTopicConfig> stateChangelogTopics = new HashMap<>();
            for (final String node : entry.getValue()) {
                // if the node is a source node, add to the source topics
                final List<String> topics = nodeToSourceTopics.get(node);
                if (topics != null) {
                    // if some of the topics are internal, add them to the internal topics
                    for (final String topic : topics) {
                        // skip global topic as they don't need partition assignment
                        if (globalTopics.contains(topic)) {
                            continue;
                        }
                        if (internalTopicNamesWithProperties.containsKey(topic)) {
                            // prefix the internal topic name with the application id
                            final String internalTopic = decorateTopic(topic);

                            final RepartitionTopicConfig repartitionTopicConfig = buildRepartitionTopicConfig(
                                internalTopic,
                                internalTopicNamesWithProperties.get(topic).getNumberOfPartitions()
                            );

                            repartitionTopics.put(repartitionTopicConfig.name(), repartitionTopicConfig);
                            sourceTopics.add(repartitionTopicConfig.name());
                        } else {
                            sourceTopics.add(topic);
                        }
                    }
                }

                // if the node is a sink node, add to the sink topics
                final String topic = nodeToSinkTopic.get(node);
                if (topic != null) {
                    if (internalTopicNamesWithProperties.containsKey(topic)) {
                        // prefix the change log topic name with the application id
                        sinkTopics.add(decorateTopic(topic));
                    } else {
                        sinkTopics.add(topic);
                    }
                }

                // if the node is connected to a state store whose changelog topics are not predefined,
                // add to the changelog topics
                for (final StoreFactory stateFactory : stateFactories.values()) {
                    if (stateFactory.connectedProcessorNames().contains(node) && storeToChangelogTopic.containsKey(stateFactory.name())) {
                        final String topicName = storeToChangelogTopic.get(stateFactory.name());
                        if (!stateChangelogTopics.containsKey(topicName)) {
                            final InternalTopicConfig internalTopicConfig =
                                createChangelogTopicConfig(stateFactory, topicName);
                            stateChangelogTopics.put(topicName, internalTopicConfig);
                        }
                    }
                }
            }
            if (!sourceTopics.isEmpty()) {
                topicGroups.put(new Subtopology(entry.getKey(), topologyName), new TopicsInfo(
                        Collections.unmodifiableSet(sinkTopics),
                        Collections.unmodifiableSet(sourceTopics),
                        Collections.unmodifiableMap(repartitionTopics),
                        Collections.unmodifiableMap(stateChangelogTopics)));
            }
        }

        return Collections.unmodifiableMap(topicGroups);
    }
Returns the map of topic groups keyed by the group id.
A topic group is a group of topics in the same task.

@return groups of topic names
streams/src/main/java/org/apache/kafka/streams/processor/internals/InternalTopologyBuilder.java