# Preview API

Show preview API for:

- 478: Key Derivation Function API (Preview)
- 487: Scoped Values (Fourth Preview)
- 494: Module Import Declarations (Second Preview)
- 499: Structured Concurrency (Fourth Preview)
- Toggle all

## Contents

- Interfaces
- Classes
- Enum Classes
- Exception Classes
- Methods
- Enum Constants

- Interfaces
  Interface
  Preview Feature
  Description
  java.lang.ScopedValue.CallableOpPREVIEW
  Scoped Values
  An operation that returns a result and may throw an exception.
  java.util.concurrent.StructuredTaskScope.SubtaskPREVIEW
  Structured Concurrency
  Represents a subtask forked with `StructuredTaskScope.fork(Callable)`PREVIEW.
  javax.crypto.KDFParametersPREVIEW
  Key Derivation Function API
  A specification of Key Derivation Function (`KDF`PREVIEW) parameters.
  javax.crypto.spec.HKDFParameterSpecPREVIEW
  Key Derivation Function API
  Parameters for the combined Extract, Expand, or Extract-then-Expand operations of the HMAC-based Key Derivation Function (HKDF).

- Classes
  Class
  Preview Feature
  Description
  java.lang.ScopedValuePREVIEW
  Scoped Values
  A value that may be safely and efficiently shared to methods without using method parameters.
  java.lang.ScopedValue.CarrierPREVIEW
  Scoped Values
  A mapping of scoped values, as keys, to values.
  java.util.concurrent.StructuredTaskScopePREVIEW
  Structured Concurrency
  A basic API for structured concurrency.
  java.util.concurrent.StructuredTaskScope.ShutdownOnFailurePREVIEW
  Structured Concurrency
  A `StructuredTaskScope` that captures the exception of the first subtask to failPREVIEW.
  java.util.concurrent.StructuredTaskScope.ShutdownOnSuccessPREVIEW
  Structured Concurrency
  A `StructuredTaskScope` that captures the result of the first subtask to complete successfullyPREVIEW.
  javax.crypto.KDFPREVIEW
  Key Derivation Function API
  This class provides the functionality of a Key Derivation Function (KDF), which is a cryptographic algorithm for deriving additional keys from input keying material (IKM) and (optionally) other data.
  javax.crypto.KDFSpiPREVIEW
  Key Derivation Function API
  This class defines the Service Provider Interface (SPI) for the Key Derivation Function (`KDF`PREVIEW) class.
  javax.crypto.spec.HKDFParameterSpec.BuilderPREVIEW
  Key Derivation Function API
  This `Builder` builds `Extract` and `ExtractThenExpand` objects.
  javax.crypto.spec.HKDFParameterSpec.ExpandPREVIEW
  Key Derivation Function API
  Defines the input parameters of an Expand operation as defined in RFC 5869.
  javax.crypto.spec.HKDFParameterSpec.ExtractPREVIEW
  Key Derivation Function API
  Defines the input parameters of an Extract operation as defined in RFC 5869.
  javax.crypto.spec.HKDFParameterSpec.ExtractThenExpandPREVIEW
  Key Derivation Function API
  Defines the input parameters of an Extract-then-Expand operation as defined in RFC 5869.

- Enum Classes
  Enum Class
  Preview Feature
  Description
  java.util.concurrent.StructuredTaskScope.Subtask.StatePREVIEW
  Structured Concurrency
  Represents the state of a subtask.

- Exception Classes
  Exception Class
  Preview Feature
  Description
  java.util.concurrent.StructureViolationExceptionPREVIEW
  Structured Concurrency
  Thrown when a structure violation is detected.

- Methods
  Method
  Preview Feature
  Description
  com.sun.source.tree.ImportTree.isModule()PREVIEW
  Module Import Declarations
  Returns true if this is an module import declaration..

- Enum Constants
  Enum Constant
  Preview Feature
  Description
  jdk.jshell.Snippet.SubKind.MODULE_IMPORT_SUBKINDPREVIEW
  Module Import Declarations
  Import Module Declaration.