Interface StructuredTaskScope.Subtask<T>

Type Parameters:
T - the result type
All Superinterfaces:
Supplier<T>
Enclosing interface:
StructuredTaskScopePREVIEW<T, R, R_X extends Throwable>
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 in a StructuredTaskScopePREVIEW with fork(Callable)PREVIEW or fork(Runnable)PREVIEW.

The scope owner can use the get() method after joiningPREVIEW 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

  • 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 the scope is cancelled, the subtask completed successfully before the scope was cancelled. If the subtask was forked with fork(Callable)PREVIEW then the result from the call() method is returned. If the subtask was forked with fork(Runnable)PREVIEW then null is returned.

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

      Code executing in the Joiner onComplete(Subtask)PREVIEW method should test that the state is SUCCESSPREVIEW before using this method to get the result.

      This method may be invoked by any thread after the scope owner has joined. The only case where this method can be used to get the result before the scope owner has joined is when called from the onComplete(Subtask) method.

      Specified by:
      get in interface Supplier<T>
      Returns:
      the possibly-null result
      Throws:
      IllegalStateException - if the subtask has not completed or did not complete successfully, or this method is invoked outside the context of the onComplete(Subtask) method before the owner thread has joined
      See Also:

    • exception

      Throwable exception()
      Returns the exception or error thrown by this subtask if it failed. If the scope is cancelled, the subtask failed before the scope was cancelled. If the subtask was forked with fork(Callable)PREVIEW then the exception or error thrown by the call() method is returned. If the subtask was forked with fork(Runnable)PREVIEW then the exception or error 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 after it has joinedPREVIEW.

      Code executing in a Joiner onComplete(Subtask)PREVIEW method should test that the state is FAILEDPREVIEW before using this method to get the exception.

      This method may be invoked by any thread after the scope owner has joined. The only case where this method can be used to get the exception before the scope owner has joined is when called from the onComplete(Subtask) method.

      Returns:
      the exception or error thrown by this subtask if it failed
      Throws:
      IllegalStateException - if the subtask has not completed or completed with a result, or this method is invoked outside the context of the onComplete(Subtask) method before the owner thread has joined
      See Also: