Uses of Class
java.util.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.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.
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.
Classes to support low-level and efficient foreign memory/function access, directly from Java.
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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 anOptional
containing the nominal descriptor for this instance.Byte.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance.Character.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance.Class.describeConstable()
Returns a nominal descriptor for this instance, if one can be constructed, or an emptyOptional
if one cannot be.Double.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance, which is the instance itself.final Optional<Enum.EnumDesc<E>>
Enum.describeConstable()
Returns an enum descriptorEnumDesc
for this instance, if one can be constructed, or an emptyOptional
if one cannot be.Float.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance, which is the instance itself.Integer.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance, which is the instance itself.Long.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance, which is the instance itself.Short.describeConstable()
Returns anOptional
containing the nominal descriptor for this instance.String.describeConstable()
Returns anOptional
containing 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
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Uses of Optional in java.lang.invoke
Modifier and TypeMethodDescriptionMethodHandle.describeConstable()
Return a nominal descriptor for this instance, if one can be constructed, or an emptyOptional
if one cannot be.MethodType.describeConstable()
Returns a nominal descriptor for this instance, if one can be constructed, or an emptyOptional
if one cannot be.VarHandle.describeConstable()
Return a nominal descriptor for this instance, if one can be constructed, or an emptyOptional
if one cannot be. -
Uses of Optional in java.lang.module
Modifier 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 anOptional
containing theSSLSession
in use on the original connection that retrieved the network resource. -
Uses of Optional in java.net.http
Modifier and TypeMethodDescriptionabstract Optional<Authenticator>
HttpClient.authenticator()
Returns anOptional
containing theAuthenticator
set on this client.abstract Optional<HttpRequest.BodyPublisher>
HttpRequest.bodyPublisher()
Returns anOptional
containing theHttpRequest.BodyPublisher
set on this request.HttpClient.connectTimeout()
Returns anOptional
containing the connect timeout duration for this client.abstract Optional<CookieHandler>
HttpClient.cookieHandler()
Returns anOptional
containing this client'sCookieHandler
.HttpClient.executor()
Returns anOptional
containing this client'sExecutor
.HttpHeaders.firstValue
(String name) Returns anOptional
containing the first header string value of the given named (and possibly multi-valued) header.HttpResponse.previousResponse()
Returns anOptional
containing the previous intermediate response if one was received.abstract Optional<ProxySelector>
HttpClient.proxy()
Returns anOptional
containing theProxySelector
supplied to this client.HttpResponse.sslSession()
Returns anOptional
containing theSSLSession
in effect for this response.HttpRequest.timeout()
Returns anOptional
containing this request's timeout duration.abstract Optional<HttpClient.Version>
HttpRequest.version()
Returns anOptional
containing the HTTP protocol version that will be requested for thisHttpRequest
.Modifier 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 aBodySubscriber
which provides the incoming body data to the provided Consumer ofOptional<byte[]>
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Uses of Optional in java.security.interfaces
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Uses of Optional in java.security.spec
Modifier 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 emptyOptional
instance.If a value is present, and the value matches the given predicate, returns anOptional
describing 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 anOptional
describing (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 anOptional
describing the given non-null
value.static <T> Optional<T>
Optional.ofNullable
(T value) Returns anOptional
describing the given value, if non-null
, otherwise returns an emptyOptional
.If a value is present, returns anOptional
describing the value, otherwise returns anOptional
produced 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 anOptional
describing the value, otherwise returns anOptional
produced by the supplying function. -
Uses of Optional in java.util.spi
Modifier and TypeMethodDescriptionstatic Optional<ToolProvider>
Returns the first instance of aToolProvider
with the given name, as loaded byServiceLoader
using the system class loader. -
Uses of Optional in java.util.stream
Modifier and TypeMethodDescriptionStream.findAny()
Returns anOptional
describing some element of the stream, or an emptyOptional
if the stream is empty.Stream.findFirst()
Returns anOptional
describing the first element of this stream, or an emptyOptional
if 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 anOptional
describing the reduced value, if any.Modifier and TypeMethodDescriptionCollectors.maxBy
(Comparator<? super T> comparator) Returns aCollector
that produces the maximal element according to a givenComparator
, described as anOptional<T>
.Collectors.minBy
(Comparator<? super T> comparator) Returns aCollector
that produces the minimal element according to a givenComparator
, described as anOptional<T>
.Collectors.reducing
(BinaryOperator<T> op) Returns aCollector
which performs a reduction of its input elements under a specifiedBinaryOperator
. -
Uses of Optional in javax.naming.ldap.spi
Modifier and TypeMethodDescriptionabstract Optional<LdapDnsProviderResult>
LdapDnsProvider.lookupEndpoints
(String url, Map<?, ?> env) Lookup the endpoints and domain name for the givenContext
provider URL
and environment. -
Uses of Optional in javax.net.ssl
Modifier and TypeMethodDescriptionHttpsURLConnection.getSSLSession()
Returns anOptional
containing theSSLSession
in use on this connection. -
Uses of Optional in jdk.incubator.foreign
Modifier and TypeMethodDescriptionReturns the attribute with the given name (if it exists).Returns the attribute with the given name (if it exists).FunctionDescriptor.describeConstable()
GroupLayout.describeConstable()
Optional<? extends DynamicConstantDesc<? extends MemoryLayout>>
MemoryLayout.describeConstable()
SequenceLayout.describeConstable()
ValueLayout.describeConstable()
Looks up a symbol with given name in this lookup.MemoryLayout.name()
Return the name (if any) associated with this layout.FunctionDescriptor.returnLayout()
Returns the return layout associated with this function.