### Question:
KafkaAdminClient extends AdminClient { static <K, V> List<V> getOrCreateListValue(Map<K, List<V>> map, K key) { List<V> list = map.get(key); if (list != null) return list; list = new LinkedList<>(); map.put(key, list); return list; } private  KafkaAdminClient(AdminClientConfig config, String clientId, Time time, Metadata metadata,
                     Metrics metrics, KafkaClient client, TimeoutProcessorFactory timeoutProcessorFactory); @Override void close(long duration, TimeUnit unit); @Override CreateTopicsResult createTopics(final Collection<NewTopic> newTopics,
                                           final CreateTopicsOptions options); @Override DeleteTopicsResult deleteTopics(final Collection<String> topicNames,
                                           DeleteTopicsOptions options); @Override ListTopicsResult listTopics(final ListTopicsOptions options); @Override DescribeTopicsResult describeTopics(final Collection<String> topicNames, DescribeTopicsOptions options); @Override DescribeClusterResult describeCluster(DescribeClusterOptions options); @Override DescribeAclsResult describeAcls(final AclBindingFilter filter, DescribeAclsOptions options); @Override CreateAclsResult createAcls(Collection<AclBinding> acls, CreateAclsOptions options); @Override DeleteAclsResult deleteAcls(Collection<AclBindingFilter> filters, DeleteAclsOptions options); @Override DescribeConfigsResult describeConfigs(Collection<ConfigResource> configResources, final DescribeConfigsOptions options); @Override AlterConfigsResult alterConfigs(Map<ConfigResource, Config> configs, final AlterConfigsOptions options);  }### Answer:
@Test public void testGetOrCreateListValue() { Map<String, List<String>> map = new HashMap<>(); List<String> fooList = KafkaAdminClient.getOrCreateListValue(map, "foo"); assertNotNull(fooList); fooList.add("a"); fooList.add("b"); List<String> fooList2 = KafkaAdminClient.getOrCreateListValue(map, "foo"); assertEquals(fooList, fooList2); assertTrue(fooList2.contains("a")); assertTrue(fooList2.contains("b")); List<String> barList = KafkaAdminClient.getOrCreateListValue(map, "bar"); assertNotNull(barList); assertTrue(barList.isEmpty()); }