Uses of Class
java.util.Optional
Packages that use Optional
Package
Description
Provides classes that are fundamental to the design of the Java
programming language.
Classes and interfaces to represent nominal descriptors for run-time
entities such as classes or method handles, and classfile entities such as
constant pool entries or
invokedynamic call sites.Provides low-level access to memory and functions outside the Java runtime.
The
java.lang.invoke package provides low-level primitives for interacting
with the Java Virtual Machine.Classes to support module descriptors and creating configurations of modules
by means of resolution and service binding.
Provides the classes for implementing networking applications.
HTTP Client and WebSocket APIs
Provides interfaces for generating RSA (Rivest, Shamir and
Adleman AsymmetricCipher algorithm)
keys as defined in the RSA Laboratory Technical Note
PKCS#1, and DSA (Digital Signature
Algorithm) keys as defined in NIST's FIPS-186.
Provides classes and interfaces for key specifications and algorithm
parameter specifications.
Contains the collections framework, some internationalization support classes,
a service loader, properties, random number generation, string parsing
and scanning classes, base64 encoding and decoding, a bit array, and
several miscellaneous utility classes.
Utility classes commonly useful in concurrent programming.
Service provider classes for the classes in the java.util package.
Classes to support functional-style operations on streams of elements, such
as map-reduce transformations on collections.
Provides classes for the secure socket package.
Defines the Service Provider Interface for pluggable JShell execution engines.
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Uses of Optional in java.lang
Modifier and TypeMethodDescriptionProcessHandle.Info.arguments()Returns an array of Strings of the arguments of the process.Runtime.Version.build()Returns the build number.ProcessHandle.Info.command()Returns the executable pathname of the process.ProcessHandle.Info.commandLine()Returns the command line of the process.Boolean.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance.Byte.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance.Character.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance.Class.describeConstable()Returns a nominal descriptor for this instance, if one can be constructed, or an emptyOptionalif one cannot be.Double.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance, which is the instance itself.final Optional<Enum.EnumDesc<E>> Enum.describeConstable()Returns an enum descriptorEnumDescfor this instance, if one can be constructed, or an emptyOptionalif one cannot be.Float.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance, which is the instance itself.Integer.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance, which is the instance itself.Long.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance, which is the instance itself.Short.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance.String.describeConstable()Returns anOptionalcontaining the nominal descriptor for this instance, which is the instance itself.ModuleLayer.findModule(String name) Returns the module with the given name in this layer, or if not in this layer, the parent layers.static Optional<ProcessHandle> ProcessHandle.of(long pid) Returns anOptional<ProcessHandle>for an existing native process.Runtime.Version.optional()Returns optional additional identifying build information.ProcessHandle.parent()Returns anOptional<ProcessHandle>for the parent process.Runtime.Version.pre()Returns the optional pre-release information.ProcessHandle.Info.startInstant()Returns the start time of the process.ProcessHandle.Info.totalCpuDuration()Returns the total cputime accumulated of the process.ProcessHandle.Info.user()Return the user of the process. -
Uses of Optional in java.lang.constant
Methods in java.lang.constant that return Optional -
Uses of Optional in java.lang.foreign
Methods in java.lang.foreign that return OptionalModifier and TypeMethodDescriptionMemorySegment.asOverlappingSlice(MemorySegmentPREVIEW other) Returns a slice of this segment that is the overlap between this and the provided segment.Returns the address of the symbol with the given name.MemorySegment.heapBase()Returns the Java object stored in the on-heap region of memory backing this memory segment, if any.MemoryLayout.name()Returns the name (if any) associated with this layout.FunctionDescriptor.returnLayout()Returns the return layout (if any) of this function descriptor.AddressLayout.targetLayout()Returns the target layout associated with this address layout (if any). -
Uses of Optional in java.lang.invoke
Methods in java.lang.invoke that return OptionalModifier and TypeMethodDescriptionMethodHandle.describeConstable()Return a nominal descriptor for this instance, if one can be constructed, or an emptyOptionalif one cannot be.MethodType.describeConstable()Returns a nominal descriptor for this instance, if one can be constructed, or an emptyOptionalif one cannot be.VarHandle.describeConstable()Return a nominal descriptor for this instance, if one can be constructed, or an emptyOptionalif one cannot be. -
Uses of Optional in java.lang.module
Methods in java.lang.module that return OptionalModifier and TypeMethodDescriptionModuleDescriptor.Requires.compiledVersion()Returns the version of the module if recorded at compile-time.Finds a reference to a module of a given name.Finds a resource, returning a URI to the resource in the module.Configuration.findModule(String name) Finds a resolved module in this configuration, or if not in this configuration, the parent configurations.ModuleReference.location()Returns the location of this module's content, if known.ModuleDescriptor.mainClass()Returns the module main class.default Optional<InputStream> Opens a resource, returning an input stream to read the resource in the module.ModuleDescriptor.Requires.rawCompiledVersion()Returns the string with the possibly-unparseable version of the module if recorded at compile-time.ModuleDescriptor.rawVersion()Returns the string with the possibly-unparseable version of the module.default Optional<ByteBuffer> Reads a resource, returning a byte buffer with the contents of the resource.ModuleDescriptor.version()Returns the module version. -
Uses of Optional in java.net
Modifier and TypeMethodDescriptionSecureCacheResponse.getSSLSession()Returns anOptionalcontaining theSSLSessionin use on the original connection that retrieved the network resource. -
Uses of Optional in java.net.http
Methods in java.net.http that return OptionalModifier and TypeMethodDescriptionabstract Optional<Authenticator> HttpClient.authenticator()Returns anOptionalcontaining theAuthenticatorset on this client.abstract Optional<HttpRequest.BodyPublisher> HttpRequest.bodyPublisher()Returns anOptionalcontaining theHttpRequest.BodyPublisherset on this request.HttpClient.connectTimeout()Returns anOptionalcontaining the connect timeout duration for this client.abstract Optional<CookieHandler> HttpClient.cookieHandler()Returns anOptionalcontaining this client'sCookieHandler.HttpClient.executor()Returns anOptionalcontaining this client'sExecutor.HttpHeaders.firstValue(String name) Returns anOptionalcontaining the first header string value of the given named (and possibly multi-valued) header.HttpResponse.previousResponse()Returns anOptionalcontaining the previous intermediate response if one was received.abstract Optional<ProxySelector> HttpClient.proxy()Returns anOptionalcontaining theProxySelectorsupplied to this client.HttpResponse.sslSession()Returns anOptionalcontaining theSSLSessionin effect for this response.HttpRequest.timeout()Returns anOptionalcontaining this request's timeout duration.abstract Optional<HttpClient.Version> HttpRequest.version()Returns anOptionalcontaining the HTTP protocol version that will be requested for thisHttpRequest.Method parameters in java.net.http with type arguments of type OptionalModifier and TypeMethodDescriptionstatic HttpResponse.BodyHandler<Void> HttpResponse.BodyHandlers.ofByteArrayConsumer(Consumer<Optional<byte[]>> consumer) Returns aBodyHandler<Void>that returns aBodySubscriber<Void>obtained fromBodySubscribers.ofByteArrayConsumer(Consumer).static HttpResponse.BodySubscriber<Void> HttpResponse.BodySubscribers.ofByteArrayConsumer(Consumer<Optional<byte[]>> consumer) Returns aBodySubscriberwhich provides the incoming body data to the provided Consumer ofOptional<byte[]>. -
Uses of Optional in java.security.interfaces
Methods in java.security.interfaces that return Optional -
Uses of Optional in java.security.spec
Methods in java.security.spec that return OptionalModifier and TypeMethodDescriptionOptional<byte[]> EdDSAParameterSpec.getContext()Get the context that the signature will use. -
Uses of Optional in java.util
Modifier and TypeMethodDescriptionstatic <T> Optional<T> Optional.empty()Returns an emptyOptionalinstance.If a value is present, and the value matches the given predicate, returns anOptionaldescribing the value, otherwise returns an emptyOptional.ServiceLoader.findFirst()Load the first available service provider of this loader's service.<U> Optional<U> If a value is present, returns the result of applying the givenOptional-bearing mapping function to the value, otherwise returns an emptyOptional.<U> Optional<U> If a value is present, returns anOptionaldescribing (as if byofNullable(T)) the result of applying the given mapping function to the value, otherwise returns an emptyOptional.static <T> Optional<T> Optional.of(T value) Returns anOptionaldescribing the given non-nullvalue.static <T> Optional<T> Optional.ofNullable(T value) Returns anOptionaldescribing the given value, if non-null, otherwise returns an emptyOptional.If a value is present, returns anOptionaldescribing the value, otherwise returns anOptionalproduced by the supplying function.Modifier and TypeMethodDescription<U> Optional<U> If a value is present, returns the result of applying the givenOptional-bearing mapping function to the value, otherwise returns an emptyOptional.If a value is present, returns anOptionaldescribing the value, otherwise returns anOptionalproduced by the supplying function. -
Uses of Optional in java.util.concurrent
Methods in java.util.concurrent that return Optional -
Uses of Optional in java.util.spi
Methods in java.util.spi that return OptionalModifier and TypeMethodDescriptionToolProvider.description()Returns a short description of the tool, or an emptyOptionalif no description is available.static Optional<ToolProvider> Returns the first instance of aToolProviderwith the given name, as loaded byServiceLoaderusing the system class loader. -
Uses of Optional in java.util.stream
Methods in java.util.stream that return OptionalModifier and TypeMethodDescriptionStream.findAny()Returns anOptionaldescribing some element of the stream, or an emptyOptionalif the stream is empty.Stream.findFirst()Returns anOptionaldescribing the first element of this stream, or an emptyOptionalif the stream is empty.Stream.max(Comparator<? super T> comparator) Returns the maximum element of this stream according to the providedComparator.Stream.min(Comparator<? super T> comparator) Returns the minimum element of this stream according to the providedComparator.Stream.reduce(BinaryOperator<T> accumulator) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns anOptionaldescribing the reduced value, if any.Methods in java.util.stream that return types with arguments of type OptionalModifier and TypeMethodDescriptionCollectors.maxBy(Comparator<? super T> comparator) Returns aCollectorthat produces the maximal element according to a givenComparator, described as anOptional<T>.Collectors.minBy(Comparator<? super T> comparator) Returns aCollectorthat produces the minimal element according to a givenComparator, described as anOptional<T>.Collectors.reducing(BinaryOperator<T> op) Returns aCollectorwhich performs a reduction of its input elements under a specifiedBinaryOperator. -
Uses of Optional in javax.naming.ldap.spi
Methods in javax.naming.ldap.spi that return OptionalModifier and TypeMethodDescriptionabstract Optional<LdapDnsProviderResult> LdapDnsProvider.lookupEndpoints(String url, Map<?, ?> env) Lookup the endpoints and domain name for the givenContextprovider URLand environment. -
Uses of Optional in javax.net.ssl
Methods in javax.net.ssl that return OptionalModifier and TypeMethodDescriptionHttpsURLConnection.getSSLSession()Returns anOptionalcontaining theSSLSessionin use on this connection. -
Uses of Optional in jdk.jshell.spi
Methods in jdk.jshell.spi that return OptionalModifier and TypeMethodDescriptiondefault Optional<JShellConsole> ExecutionEnv.console()Returns theJShellConsolethat should be used by the execution engine, ornullif none.