本文整理了Java中java.util.Collections.emptySet()方法的一些代码示例，展示了Collections.emptySet()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。Collections.emptySet()方法的具体详情如下：
包路径：java.util.Collections
类名称：Collections
方法名：emptySet

Collections.emptySet介绍

[英]Returns a type-safe empty, immutable Set.
[中]返回类型安全的空不可变集。

代码示例

代码示例来源：origin: spring-projects/spring-framework

@Override
public Set<String> getMetaAnnotationTypes(String annotationName) {
  Set<String> metaAnnotationTypes = this.metaAnnotationMap.get(annotationName);
  return (metaAnnotationTypes != null ? metaAnnotationTypes : Collections.emptySet());
}

代码示例来源：origin: square/retrofit

private static Set<? extends Annotation> jsonAnnotations(Annotation[] annotations) {
  Set<Annotation> result = null;
  for (Annotation annotation : annotations) {
   if (annotation.annotationType().isAnnotationPresent(JsonQualifier.class)) {
    if (result == null) result = new LinkedHashSet<>();
    result.add(annotation);
   }
  }
  return result != null ? unmodifiableSet(result) : Collections.<Annotation>emptySet();
 }
}

代码示例来源：origin: jenkinsci/jenkins

@Override
  protected Iterable<? extends String> getEdges(String n) {
    // return variables referred from the variable.
    if (!refereeSetMap.containsKey(n)) {
      // there is a case a non-existing variable is referred...
      return Collections.emptySet();
    }
    return refereeSetMap.get(n);
  }
};

代码示例来源：origin: apache/geode

Set getDependencySet(CompiledValue cv, boolean readOnly) {
 Set set = (Set) this.dependencyGraph.get(cv);
 if (set == null) {
  if (readOnly)
   return Collections.emptySet();
  set = new HashSet(1);
  this.dependencyGraph.put(cv, set);
 }
 return set;
}

代码示例来源：origin: square/okhttp

/**
 * Returns the distinct query parameter names in this URL, like {@code ["a", "b"]} for {@code
 * http://host/?a=apple&b=banana}. If this URL has no query this returns the empty set.
 *
 * <p><table summary="">
 *   <tr><th>URL</th><th>{@code queryParameterNames()}</th></tr>
 *   <tr><td>{@code http://host/}</td><td>{@code []}</td></tr>
 *   <tr><td>{@code http://host/?}</td><td>{@code [""]}</td></tr>
 *   <tr><td>{@code http://host/?a=apple&k=key+lime}</td><td>{@code ["a", "k"]}</td></tr>
 *   <tr><td>{@code http://host/?a=apple&a=apricot}</td><td>{@code ["a"]}</td></tr>
 *   <tr><td>{@code http://host/?a=apple&b}</td><td>{@code ["a", "b"]}</td></tr>
 * </table>
 */
public Set<String> queryParameterNames() {
 if (queryNamesAndValues == null) return Collections.emptySet();
 Set<String> result = new LinkedHashSet<>();
 for (int i = 0, size = queryNamesAndValues.size(); i < size; i += 2) {
  result.add(queryNamesAndValues.get(i));
 }
 return Collections.unmodifiableSet(result);
}

代码示例来源：origin: skylot/jadx

private Set<String> getAncestors(String clsName) {
  Set<String> result = ancestorCache.get(clsName);
  if (result != null) {
    return result;
  }
  NClass cls = nameMap.get(clsName);
  if (cls == null) {
    missingClasses.add(clsName);
    return Collections.emptySet();
  }
  result = new HashSet<>();
  addAncestorsNames(cls, result);
  if (result.isEmpty()) {
    result = Collections.emptySet();
  }
  ancestorCache.put(clsName, result);
  return result;
}

代码示例来源：origin: spring-projects/spring-framework

public Collection<SourceClass> getAnnotationAttributes(String annType, String attribute) throws IOException {
  Map<String, Object> annotationAttributes = this.metadata.getAnnotationAttributes(annType, true);
  if (annotationAttributes == null || !annotationAttributes.containsKey(attribute)) {
    return Collections.emptySet();
  }
  String[] classNames = (String[]) annotationAttributes.get(attribute);
  Set<SourceClass> result = new LinkedHashSet<>();
  for (String className : classNames) {
    result.add(getRelated(className));
  }
  return result;
}

代码示例来源：origin: pmd/pmd

private Set<String> styleForDepth(int depth, boolean inlineHighlight) {
  if (depth < 0) {
    // that's the style when we're outside any node
    return Collections.emptySet();
  } else {
    // Caching reduces the number of sets used by this step of the overlaying routine to
    // only a few. The number is probably blowing up during the actual spans overlaying
    // in StyleContext#recomputePainting
    DEPTH_STYLE_CACHE.putIfAbsent(style, new HashMap<>());
    Map<Integer, Map<Boolean, Set<String>>> depthToStyle = DEPTH_STYLE_CACHE.get(style);
    depthToStyle.putIfAbsent(depth, new HashMap<>());
    Map<Boolean, Set<String>> isInlineToStyle = depthToStyle.get(depth);
    if (isInlineToStyle.containsKey(inlineHighlight)) {
      return isInlineToStyle.get(inlineHighlight);
    }
    Set<String> s = new HashSet<>(style);
    s.add("depth-" + depth);
    if (inlineHighlight) {
      // inline highlight can be used to add boxing around a node if it wouldn't be ugly
      s.add("inline-highlight");
    }
    isInlineToStyle.put(inlineHighlight, s);
    return s;
  }
}

代码示例来源：origin: alibaba/cobar

/**
   * @param orig if null, return intersect
   */
  public static Set<? extends Object> intersectSet(Set<? extends Object> orig, Set<? extends Object> intersect) {
    if (orig == null)
      return intersect;
    if (intersect == null || orig.isEmpty())
      return Collections.emptySet();
    Set<Object> set = new HashSet<Object>(orig.size());
    for (Object p : orig) {
      if (intersect.contains(p))
        set.add(p);
    }
    return set;
  }
}

代码示例来源：origin: bumptech/glide

if (values.size() != 1) {
 throw new IllegalArgumentException("Expected single value, but found: " + values);
return Collections.emptySet();
Set<String> result = new HashSet<>(values.size());
for (Object current : values) {
 result.add(getExcludedModuleClassFromAnnotationAttribute(clazz, current));
return Collections.singleton(classType.toString());

代码示例来源：origin: qunarcorp/qmq

public Set<ClientMetaInfo> aliveClientsOf(String subject) {
  final Map<ClientMetaInfo, Long> clients = allClients.get(subject);
  if (clients == null || clients.isEmpty()) {
    return Collections.emptySet();
  }
  final long now = System.currentTimeMillis();
  final Set<ClientMetaInfo> result = new HashSet<>();
  for (Map.Entry<ClientMetaInfo, Long> entry : clients.entrySet()) {
    if (entry.getValue() != null && now - entry.getValue() < EXPIRE_TIME_MS) {
      result.add(entry.getKey());
    }
  }
  return result;
}

代码示例来源：origin: spring-projects/spring-security-oauth

public OAuth2Authentication extractAuthentication(Map<String, ?> map) {
  Map<String, String> parameters = new HashMap<String, String>();
  Set<String> scope = extractScope(map);
  Authentication user = userTokenConverter.extractAuthentication(map);
  String clientId = (String) map.get(clientIdAttribute);
  parameters.put(clientIdAttribute, clientId);
  if (includeGrantType && map.containsKey(GRANT_TYPE)) {
    parameters.put(GRANT_TYPE, (String) map.get(GRANT_TYPE));
  }
  Set<String> resourceIds = new LinkedHashSet<String>(map.containsKey(AUD) ? getAudience(map)
      : Collections.<String>emptySet());
  
  Collection<? extends GrantedAuthority> authorities = null;
  if (user==null && map.containsKey(AUTHORITIES)) {
    @SuppressWarnings("unchecked")
    String[] roles = ((Collection<String>)map.get(AUTHORITIES)).toArray(new String[0]);
    authorities = AuthorityUtils.createAuthorityList(roles);
  }
  OAuth2Request request = new OAuth2Request(parameters, clientId, authorities, true, scope, resourceIds, null, null,
      null);
  return new OAuth2Authentication(request, user);
}

代码示例来源：origin: apache/kafka

PartitionInfo part1 = new PartitionInfo(topic, 1, node1, null, null);
Cluster cluster = new Cluster(null, Collections.singletonList(node1), Collections.singletonList(part1),
    Collections.emptySet(), Collections.emptySet());
accumulator.append(tp1, time.milliseconds(), "key".getBytes(),
    "value".getBytes(), Record.EMPTY_HEADERS, null, MAX_BLOCK_TIMEOUT);
Map<Integer, List<ProducerBatch>> drainedBatches = accumulator.drain(cluster, Collections.singleton(node1),
    Integer.MAX_VALUE,
    time.milliseconds());
assertTrue(drainedBatches.containsKey(node1.id()));
assertEquals(1, drainedBatches.get(node1.id()).size());
assertTrue(transactionManager.hasAbortableError());

代码示例来源：origin: wildfly/wildfly

@Override
public Set<InetSocketAddress> allLocalAddresses() {
  try {
    final Set<SocketAddress> allLocalAddresses = sch.getAllLocalAddresses();
    final Set<InetSocketAddress> addresses = new LinkedHashSet<InetSocketAddress>(allLocalAddresses.size());
    for (SocketAddress socketAddress : allLocalAddresses) {
      addresses.add((InetSocketAddress) socketAddress);
    }
    return addresses;
  } catch (Throwable ignored) {
    return Collections.emptySet();
  }
}

代码示例来源：origin: apache/kafka

@Test
public void testDeleteConsumerGroups() throws Exception {
  final HashMap<Integer, Node> nodes = new HashMap<>();
  nodes.put(0, new Node(0, "localhost", 8121));
  final Cluster cluster =
    new Cluster(
      "mockClusterId",
      nodes.values(),
      Collections.<PartitionInfo>emptyList(),
      Collections.<String>emptySet(),
      Collections.<String>emptySet(), nodes.get(0));
  final List<String> groupIds = singletonList("group-0");
  try (AdminClientUnitTestEnv env = new AdminClientUnitTestEnv(cluster)) {
    env.kafkaClient().setNodeApiVersions(NodeApiVersions.create());
    //Retriable FindCoordinatorResponse errors should be retried
    env.kafkaClient().prepareResponse(new FindCoordinatorResponse(Errors.COORDINATOR_NOT_AVAILABLE,  Node.noNode()));
    env.kafkaClient().prepareResponse(new FindCoordinatorResponse(Errors.COORDINATOR_LOAD_IN_PROGRESS, Node.noNode()));
    env.kafkaClient().prepareResponse(new FindCoordinatorResponse(Errors.NONE, env.cluster().controller()));
    final Map<String, Errors> response = new HashMap<>();
    response.put("group-0", Errors.NONE);
    env.kafkaClient().prepareResponse(new DeleteGroupsResponse(response));
    final DeleteConsumerGroupsResult result = env.adminClient().deleteConsumerGroups(groupIds);
    final KafkaFuture<Void> results = result.deletedGroups().get("group-0");
    assertNull(results.get());
    //should throw error for non-retriable errors
    env.kafkaClient().prepareResponse(new FindCoordinatorResponse(Errors.GROUP_AUTHORIZATION_FAILED,  Node.noNode()));
    final DeleteConsumerGroupsResult errorResult = env.adminClient().deleteConsumerGroups(groupIds);
    TestUtils.assertFutureError(errorResult.deletedGroups().get("group-0"), GroupAuthorizationException.class);
  }
}

代码示例来源：origin: square/okhttp

/**
 * Returns the names of the request headers that need to be checked for equality when caching.
 */
public static Set<String> varyFields(Headers responseHeaders) {
 Set<String> result = Collections.emptySet();
 for (int i = 0, size = responseHeaders.size(); i < size; i++) {
  if (!"Vary".equalsIgnoreCase(responseHeaders.name(i))) continue;
  String value = responseHeaders.value(i);
  if (result.isEmpty()) {
   result = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
  }
  for (String varyField : value.split(",")) {
   result.add(varyField.trim());
  }
 }
 return result;
}

代码示例来源：origin: org.mockito/mockito-core

private void assureCanReadMockito(Set<Class<?>> types) {
  if (redefineModule == null) {
    return;
  }
  Set<Object> modules = new HashSet<Object>();
  try {
    Object target = getModule.invoke(Class.forName("org.mockito.internal.creation.bytebuddy.inject.MockMethodDispatcher", false, null));
    for (Class<?> type : types) {
      Object module = getModule.invoke(type);
      if (!modules.contains(module) && !(Boolean) canRead.invoke(module, target)) {
        modules.add(module);
      }
    }
    for (Object module : modules) {
      redefineModule.invoke(instrumentation, module, Collections.singleton(target),
        Collections.emptyMap(), Collections.emptyMap(), Collections.emptySet(), Collections.emptyMap());
    }
  } catch (Exception e) {
    throw new IllegalStateException(join("Could not adjust module graph to make the mock instance dispatcher visible to some classes",
      "",
      "At least one of those modules: " + modules + " is not reading the unnamed module of the bootstrap loader",
      "Without such a read edge, the classes that are redefined to become mocks cannot access the mock dispatcher.",
      "To circumvent this, Mockito attempted to add a read edge to this module what failed for an unexpected reason"), e);
  }
}

代码示例来源：origin: spring-projects/spring-framework

private Set<String> getPrefixesSet(String namespaceUri) {
  Assert.notNull(namespaceUri, "No namespaceUri given");
  if (this.defaultNamespaceUri.equals(namespaceUri)) {
    return Collections.singleton(XMLConstants.DEFAULT_NS_PREFIX);
  }
  else if (XMLConstants.XML_NS_URI.equals(namespaceUri)) {
    return Collections.singleton(XMLConstants.XML_NS_PREFIX);
  }
  else if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(namespaceUri)) {
    return Collections.singleton(XMLConstants.XMLNS_ATTRIBUTE);
  }
  else {
    Set<String> prefixes = this.namespaceUriToPrefixes.get(namespaceUri);
    return (prefixes != null ?  Collections.unmodifiableSet(prefixes) : Collections.emptySet());
  }
}

代码示例来源：origin: org.netbeans.api/org-openide-filesystems

boolean canHaveRootAttributeOnReadOnlyFS(String name) {
    Set<String> tmp = rootAttributes;
    if (tmp == null) {
      tmp = new HashSet<String>();
      for (FileSystem fs : getDelegates()) {
        if (fs == null) {
          continue;
        }
        if (!fs.isReadOnly()) {
          continue;
        }
        Enumeration<String> en = fs.getRoot().getAttributes();
        while (en.hasMoreElements()) {
          tmp.add(en.nextElement());
        }
        rootAttributes = tmp;
      }
    }
    if (tmp == Collections.<String>emptySet()) {
      return true;
    }
    return tmp.contains(name);
  }
}

代码示例来源：origin: google/guava

public void testForMapRemoveAll() {
 Map<String, Integer> map = Maps.newHashMap();
 map.put("foo", 1);
 map.put("bar", 2);
 map.put("cow", 3);
 Multimap<String, Integer> multimap = Multimaps.forMap(map);
 assertEquals(3, multimap.size());
 assertEquals(Collections.emptySet(), multimap.removeAll("dog"));
 assertEquals(3, multimap.size());
 assertTrue(multimap.containsKey("bar"));
 assertEquals(Collections.singleton(2), multimap.removeAll("bar"));
 assertEquals(2, multimap.size());
 assertFalse(multimap.containsKey("bar"));
}