Interface StructuredTaskScope.Subtask<T>

Type Parameters:

T - the result type

All Superinterfaces:

Supplier<T>

Enclosing interface:

StructuredTaskScopePREVIEW<T,R>

public static sealed interface StructuredTaskScope.Subtask<T>
extends Supplier<T>

Subtask is a preview API of the Java platform.

Programs can only use Subtask when preview features are enabled.

Preview features may be removed in a future release, or upgraded to permanent features of the Java platform.

Represents a subtask forked with StructuredTaskScope.fork(Callable)^PREVIEW or StructuredTaskScope.fork(Runnable)^PREVIEW.

Code that forks subtasks can use the get() method after joining^PREVIEW to obtain the result of a subtask that completed successfully. It can use the exception() method to obtain the exception thrown by a subtask that failed.

Since:

21

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static enum	StructuredTaskScope.Subtask.StatePREVIEW	Preview. Represents the state of a subtask.

Method Summary

Modifier and Type	Method	Description
Throwable	exception()	Returns the exception thrown by this subtask if it failed.
T	get()	Returns the result of this subtask if it completed successfully.
StructuredTaskScope.Subtask.StatePREVIEW	state()	Returns the subtask state.

Method Details

state

StructuredTaskScope.Subtask.StatePREVIEW state()

Returns the subtask state.

Returns:

the subtask state

get

T get()

Returns the result of this subtask if it completed successfully. If forked^PREVIEW to execute a value-returning task then the result from the call method is returned. If forked^PREVIEW to execute a task that does not return a result then null is returned.

Code executing in the scope owner thread can use this method to get the result of a successful subtask only after it has joined^PREVIEW.

Code executing in the Joiner onComplete^PREVIEW method should test that the subtask state is SUCCESS^PREVIEW before using this method to get the result.

Specified by:

get in interface Supplier<T>

Returns:

the possibly-null result

Throws:

IllegalStateException - if the subtask has not completed, did not complete successfully, or the current thread is the scope owner invoking this method before joining^PREVIEW

See Also:

• StructuredTaskScope.Subtask.State.SUCCESS^PREVIEW

exception

Throwable exception()

Returns the exception thrown by this subtask if it failed. If forked^PREVIEW to execute a value-returning task then the exception thrown by the call method is returned. If forked^PREVIEW to execute a task that does not return a result then the exception thrown by the run method is returned.

Code executing in the scope owner thread can use this method to get the exception thrown by a failed subtask only after it has joined^PREVIEW.

Code executing in a Joiner onComplete^PREVIEW method should test that the subtask state is FAILED^PREVIEW before using this method to get the exception.

Returns:

the exception thrown by this subtask if it failed

Throws:

IllegalStateException - if the subtask has not completed, completed with a result, or the current thread is the scope owner invoking this method before joining^PREVIEW

See Also:

• StructuredTaskScope.Subtask.State.FAILED^PREVIEW