56 |
|
* exceptions such as {@code IOExceptions} to be thrown. However, |
57 |
|
* computations may still encounter unchecked exceptions, that are |
58 |
|
* rethrown to callers attempting to join them. These exceptions may |
59 |
< |
* additionally include RejectedExecutionExceptions stemming from |
60 |
< |
* internal resource exhaustion such as failure to allocate internal |
61 |
< |
* task queues. |
59 |
> |
* additionally include {@link RejectedExecutionException} stemming |
60 |
> |
* from internal resource exhaustion, such as failure to allocate |
61 |
> |
* internal task queues. |
62 |
|
* |
63 |
|
* <p>The primary method for awaiting completion and extracting |
64 |
|
* results of a task is {@link #join}, but there are several variants: |
68 |
|
* execute other tasks while awaiting joins, which is sometimes more |
69 |
|
* efficient but only applies when all subtasks are known to be |
70 |
|
* strictly tree-structured. Method {@link #invoke} is semantically |
71 |
< |
* equivalent to {@code fork(); join()} but always attempts to |
72 |
< |
* begin execution in the current thread. The "<em>quiet</em>" forms |
73 |
< |
* of these methods do not extract results or report exceptions. These |
71 |
> |
* equivalent to {@code fork(); join()} but always attempts to begin |
72 |
> |
* execution in the current thread. The "<em>quiet</em>" forms of |
73 |
> |
* these methods do not extract results or report exceptions. These |
74 |
|
* may be useful when a set of tasks are being executed, and you need |
75 |
|
* to delay processing of results or exceptions until all complete. |
76 |
|
* Method {@code invokeAll} (available in multiple versions) |
77 |
|
* performs the most common form of parallel invocation: forking a set |
78 |
|
* of tasks and joining them all. |
79 |
|
* |
80 |
+ |
* <p>The execution status of tasks may be queried at several levels |
81 |
+ |
* of detail: {@link #isDone} is true if a task completed in any way |
82 |
+ |
* (including the case where a task was cancelled without executing); |
83 |
+ |
* {@link #isCompletedNormally} is true if a task completed without |
84 |
+ |
* cancellation or encountering an exception; {@link #isCancelled} is |
85 |
+ |
* true if the task was cancelled (in which case {@link #getException} |
86 |
+ |
* returns a {@link java.util.concurrent.CancellationException}); and |
87 |
+ |
* {@link #isCompletedAbnormally} is true if a task was either |
88 |
+ |
* cancelled or encountered an exception, in which case {@link |
89 |
+ |
* #getException} will return either the encountered exception or |
90 |
+ |
* {@link java.util.concurrent.CancellationException}. |
91 |
+ |
* |
92 |
|
* <p>The ForkJoinTask class is not usually directly subclassed. |
93 |
|
* Instead, you subclass one of the abstract classes that support a |
94 |
|
* particular style of fork/join processing, typically {@link |
123 |
|
* improve throughput. If too small, then memory and internal task |
124 |
|
* maintenance overhead may overwhelm processing. |
125 |
|
* |
126 |
< |
* <p>This class provides {@code adapt} methods for {@link |
127 |
< |
* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
128 |
< |
* may be of use when mixing execution of ForkJoinTasks with other |
129 |
< |
* kinds of tasks. When all tasks are of this form, consider using a |
130 |
< |
* pool in {@link ForkJoinPool#setAsyncMode async mode}. |
126 |
> |
* <p>This class provides {@code adapt} methods for {@link Runnable} |
127 |
> |
* and {@link Callable}, that may be of use when mixing execution of |
128 |
> |
* {@code ForkJoinTasks} with other kinds of tasks. When all tasks |
129 |
> |
* are of this form, consider using a pool in |
130 |
> |
* {@linkplain ForkJoinPool#setAsyncMode async mode}. |
131 |
|
* |
132 |
|
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
133 |
|
* used in extensions such as remote execution frameworks. It is |
390 |
|
|
391 |
|
/** |
392 |
|
* Returns result or throws exception using j.u.c.Future conventions. |
393 |
< |
* Only call when {@code isDone} known to be true. |
393 |
> |
* Only call when {@code isDone} known to be true or thread known |
394 |
> |
* to be interrupted. |
395 |
|
*/ |
396 |
|
private V reportFutureResult() |
397 |
< |
throws ExecutionException, InterruptedException { |
397 |
> |
throws InterruptedException, ExecutionException { |
398 |
|
if (Thread.interrupted()) |
399 |
|
throw new InterruptedException(); |
400 |
|
int s = status & COMPLETION_MASK; |
420 |
|
int s = status & COMPLETION_MASK; |
421 |
|
if (s == NORMAL) |
422 |
|
return getRawResult(); |
423 |
< |
if (s == CANCELLED) |
423 |
> |
else if (s == CANCELLED) |
424 |
|
throw new CancellationException(); |
425 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
425 |
> |
else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
426 |
|
throw new ExecutionException(ex); |
427 |
< |
throw new TimeoutException(); |
427 |
> |
else |
428 |
> |
throw new TimeoutException(); |
429 |
|
} |
430 |
|
|
431 |
|
// internal execution methods |
511 |
|
* Arranges to asynchronously execute this task. While it is not |
512 |
|
* necessarily enforced, it is a usage error to fork a task more |
513 |
|
* than once unless it has completed and been reinitialized. |
514 |
+ |
* Subsequent modifications to the state of this task or any data |
515 |
+ |
* it operates on are not necessarily consistently observable by |
516 |
+ |
* any thread other than the one executing it unless preceded by a |
517 |
+ |
* call to {@link #join} or related methods, or a call to {@link |
518 |
+ |
* #isDone} returning {@code true}. |
519 |
|
* |
520 |
|
* <p>This method may be invoked only from within {@code |
521 |
|
* ForkJoinTask} computations (as may be determined using method |
532 |
|
} |
533 |
|
|
534 |
|
/** |
535 |
< |
* Returns the result of the computation when it is ready. |
535 |
> |
* Returns the result of the computation when it {@link #isDone is done}. |
536 |
|
* This method differs from {@link #get()} in that |
537 |
|
* abnormal completion results in {@code RuntimeException} or |
538 |
|
* {@code Error}, not {@code ExecutionException}. |
563 |
|
/** |
564 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
565 |
|
* each task or an (unchecked) exception is encountered, in which |
566 |
< |
* case the exception is rethrown. If more than one task |
567 |
< |
* encounters an exception, then this method throws any one of |
568 |
< |
* these exceptions. The individual status of each task may be |
566 |
> |
* case the exception is rethrown. If either task encounters an |
567 |
> |
* exception, the other one may be, but is not guaranteed to be, |
568 |
> |
* cancelled. If both tasks throw an exception, then this method |
569 |
> |
* throws one of them. The individual status of each task may be |
570 |
|
* checked using {@link #getException()} and related methods. |
571 |
|
* |
572 |
|
* <p>This method may be invoked only from within {@code |
729 |
|
return (status & COMPLETION_MASK) == CANCELLED; |
730 |
|
} |
731 |
|
|
712 |
– |
/** |
713 |
– |
* Returns {@code true} if the computation performed by this task |
714 |
– |
* has completed (or has been cancelled). |
715 |
– |
* |
716 |
– |
* @return {@code true} if this computation has completed |
717 |
– |
*/ |
732 |
|
public final boolean isDone() { |
733 |
|
return status < 0; |
734 |
|
} |
735 |
|
|
722 |
– |
/** |
723 |
– |
* Returns {@code true} if this task was cancelled. |
724 |
– |
* |
725 |
– |
* @return {@code true} if this task was cancelled |
726 |
– |
*/ |
736 |
|
public final boolean isCancelled() { |
737 |
|
return (status & COMPLETION_MASK) == CANCELLED; |
738 |
|
} |
758 |
|
} |
759 |
|
|
760 |
|
/** |
752 |
– |
* Returns {@code true} if this task threw an exception. |
753 |
– |
* |
754 |
– |
* @return {@code true} if this task threw an exception |
755 |
– |
*/ |
756 |
– |
public final boolean isCompletedExceptionally() { |
757 |
– |
return (status & COMPLETION_MASK) == EXCEPTIONAL; |
758 |
– |
} |
759 |
– |
|
760 |
– |
/** |
761 |
|
* Returns the exception thrown by the base computation, or a |
762 |
|
* {@code CancellationException} if cancelled, or {@code null} if |
763 |
|
* none or if the method has not yet completed. |
766 |
|
*/ |
767 |
|
public final Throwable getException() { |
768 |
|
int s = status & COMPLETION_MASK; |
769 |
< |
if (s >= NORMAL) |
770 |
< |
return null; |
771 |
< |
if (s == CANCELLED) |
772 |
< |
return new CancellationException(); |
773 |
< |
return exceptionMap.get(this); |
769 |
> |
return ((s >= NORMAL) ? null : |
770 |
> |
(s == CANCELLED) ? new CancellationException() : |
771 |
> |
exceptionMap.get(this)); |
772 |
|
} |
773 |
|
|
774 |
|
/** |
781 |
|
* overridable, but overridden versions must invoke {@code super} |
782 |
|
* implementation to maintain guarantees. |
783 |
|
* |
784 |
< |
* @param ex the exception to throw. If this exception is |
785 |
< |
* not a RuntimeException or Error, the actual exception thrown |
786 |
< |
* will be a RuntimeException with cause ex. |
784 |
> |
* @param ex the exception to throw. If this exception is not a |
785 |
> |
* {@code RuntimeException} or {@code Error}, the actual exception |
786 |
> |
* thrown will be a {@code RuntimeException} with cause {@code ex}. |
787 |
|
*/ |
788 |
|
public void completeExceptionally(Throwable ex) { |
789 |
|
setDoneExceptionally((ex instanceof RuntimeException) || |
830 |
|
} |
831 |
|
|
832 |
|
/** |
833 |
< |
* Possibly executes other tasks until this task is ready, then |
834 |
< |
* returns the result of the computation. This method may be more |
835 |
< |
* efficient than {@code join}, but is only applicable when |
836 |
< |
* there are no potential dependencies between continuation of the |
837 |
< |
* current task and that of any other task that might be executed |
838 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
839 |
< |
* tasks). |
833 |
> |
* Possibly executes other tasks until this task {@link #isDone is |
834 |
> |
* done}, then returns the result of the computation. This method |
835 |
> |
* may be more efficient than {@code join}, but is only applicable |
836 |
> |
* when there are no potential dependencies between continuation |
837 |
> |
* of the current task and that of any other task that might be |
838 |
> |
* executed while helping. (This usually holds for pure |
839 |
> |
* divide-and-conquer tasks). |
840 |
|
* |
841 |
|
* <p>This method may be invoked only from within {@code |
842 |
|
* ForkJoinTask} computations (as may be determined using method |
854 |
|
} |
855 |
|
|
856 |
|
/** |
857 |
< |
* Possibly executes other tasks until this task is ready. This |
858 |
< |
* method may be useful when processing collections of tasks when |
859 |
< |
* some have been cancelled or otherwise known to have aborted. |
857 |
> |
* Possibly executes other tasks until this task {@link #isDone is |
858 |
> |
* done}. This method may be useful when processing collections |
859 |
> |
* of tasks when some have been cancelled or otherwise known to |
860 |
> |
* have aborted. |
861 |
|
* |
862 |
|
* <p>This method may be invoked only from within {@code |
863 |
|
* ForkJoinTask} computations (as may be determined using method |