| 25 |
|
* <p> A "main" ForkJoinTask begins execution when submitted to a |
| 26 |
|
* {@link ForkJoinPool}. Once started, it will usually in turn start |
| 27 |
|
* other subtasks. As indicated by the name of this class, many |
| 28 |
< |
* programs using ForkJoinTasks employ only methods {@code fork} |
| 29 |
< |
* and {@code join}, or derivatives such as |
| 30 |
< |
* {@code invokeAll}. However, this class also provides a number |
| 31 |
< |
* of other methods that can come into play in advanced usages, as |
| 32 |
< |
* well as extension mechanics that allow support of new forms of |
| 33 |
< |
* fork/join processing. |
| 28 |
> |
* programs using ForkJoinTasks employ only methods {@code fork} and |
| 29 |
> |
* {@code join}, or derivatives such as {@code invokeAll}. However, |
| 30 |
> |
* this class also provides a number of other methods that can come |
| 31 |
> |
* into play in advanced usages, as well as extension mechanics that |
| 32 |
> |
* allow support of new forms of fork/join processing. |
| 33 |
|
* |
| 34 |
|
* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
| 35 |
|
* efficiency of ForkJoinTasks stems from a set of restrictions (that |
| 93 |
|
* lightweight task scheduling framework, and so cannot be overridden. |
| 94 |
|
* Developers creating new basic styles of fork/join processing should |
| 95 |
|
* minimally implement {@code protected} methods |
| 96 |
< |
* {@code exec}, {@code setRawResult}, and |
| 97 |
< |
* {@code getRawResult}, while also introducing an abstract |
| 96 |
> |
* {@link #exec}, {@link #setRawResult}, and |
| 97 |
> |
* {@link #getRawResult}, while also introducing an abstract |
| 98 |
|
* computational method that can be implemented in its subclasses, |
| 99 |
|
* possibly relying on other {@code protected} methods provided |
| 100 |
|
* by this class. |
| 651 |
|
} |
| 652 |
|
|
| 653 |
|
/** |
| 654 |
< |
* Returns true if the computation performed by this task has |
| 655 |
< |
* completed (or has been cancelled). |
| 654 |
> |
* Returns {@code true} if the computation performed by this task |
| 655 |
> |
* has completed (or has been cancelled). |
| 656 |
|
* |
| 657 |
< |
* @return true if this computation has completed |
| 657 |
> |
* @return {@code true} if this computation has completed |
| 658 |
|
*/ |
| 659 |
|
public final boolean isDone() { |
| 660 |
|
return status < 0; |
| 661 |
|
} |
| 662 |
|
|
| 663 |
|
/** |
| 664 |
< |
* Returns true if this task was cancelled. |
| 664 |
> |
* Returns {@code true} if this task was cancelled. |
| 665 |
|
* |
| 666 |
< |
* @return true if this task was cancelled |
| 666 |
> |
* @return {@code true} if this task was cancelled |
| 667 |
|
*/ |
| 668 |
|
public final boolean isCancelled() { |
| 669 |
|
return (status & COMPLETION_MASK) == CANCELLED; |
| 672 |
|
/** |
| 673 |
|
* Asserts that the results of this task's computation will not be |
| 674 |
|
* used. If a cancellation occurs before attempting to execute this |
| 675 |
< |
* task, then execution will be suppressed, {@code isCancelled} |
| 676 |
< |
* will report true, and {@code join} will result in a |
| 675 |
> |
* task, execution will be suppressed, {@link #isCancelled} |
| 676 |
> |
* will report true, and {@link #join} will result in a |
| 677 |
|
* {@code CancellationException} being thrown. Otherwise, when |
| 678 |
|
* cancellation races with completion, there are no guarantees |
| 679 |
< |
* about whether {@code isCancelled} will report true, whether |
| 680 |
< |
* {@code join} will return normally or via an exception, or |
| 681 |
< |
* whether these behaviors will remain consistent upon repeated |
| 679 |
> |
* about whether {@code isCancelled} will report {@code true}, |
| 680 |
> |
* whether {@code join} will return normally or via an exception, |
| 681 |
> |
* or whether these behaviors will remain consistent upon repeated |
| 682 |
|
* invocation. |
| 683 |
|
* |
| 684 |
|
* <p>This method may be overridden in subclasses, but if so, must |
| 688 |
|
* <p> This method is designed to be invoked by <em>other</em> |
| 689 |
|
* tasks. To terminate the current task, you can just return or |
| 690 |
|
* throw an unchecked exception from its computation method, or |
| 691 |
< |
* invoke {@code completeExceptionally}. |
| 691 |
> |
* invoke {@link #completeExceptionally}. |
| 692 |
|
* |
| 693 |
|
* @param mayInterruptIfRunning this value is ignored in the |
| 694 |
|
* default implementation because tasks are not in general |
| 695 |
|
* cancelled via interruption |
| 696 |
|
* |
| 697 |
< |
* @return true if this task is now cancelled |
| 697 |
> |
* @return {@code true} if this task is now cancelled |
| 698 |
|
*/ |
| 699 |
|
public boolean cancel(boolean mayInterruptIfRunning) { |
| 700 |
|
setCompletion(CANCELLED); |
| 702 |
|
} |
| 703 |
|
|
| 704 |
|
/** |
| 705 |
< |
* Returns true if this task threw an exception or was cancelled. |
| 705 |
> |
* Returns {@code true} if this task threw an exception or was cancelled. |
| 706 |
|
* |
| 707 |
< |
* @return true if this task threw an exception or was cancelled |
| 707 |
> |
* @return {@code true} if this task threw an exception or was cancelled |
| 708 |
|
*/ |
| 709 |
|
public final boolean isCompletedAbnormally() { |
| 710 |
|
return (status & COMPLETION_MASK) < NORMAL; |
| 715 |
|
* CancellationException if cancelled, or null if none or if the |
| 716 |
|
* method has not yet completed. |
| 717 |
|
* |
| 718 |
< |
* @return the exception, or null if none |
| 718 |
> |
* @return the exception, or {@code null} if none |
| 719 |
|
*/ |
| 720 |
|
public final Throwable getException() { |
| 721 |
|
int s = status & COMPLETION_MASK; |
| 878 |
|
* Returns the pool hosting the current task execution, or null |
| 879 |
|
* if this task is executing outside of any ForkJoinPool. |
| 880 |
|
* |
| 881 |
< |
* @return the pool, or null if none |
| 881 |
> |
* @return the pool, or {@code null} if none |
| 882 |
|
*/ |
| 883 |
|
public static ForkJoinPool getPool() { |
| 884 |
|
Thread t = Thread.currentThread(); |
| 909 |
|
* result in exceptions or errors, possibly including |
| 910 |
|
* ClassCastException. |
| 911 |
|
* |
| 912 |
< |
* @return true if unforked |
| 912 |
> |
* @return {@code true} if unforked |
| 913 |
|
*/ |
| 914 |
|
public boolean tryUnfork() { |
| 915 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
| 949 |
|
// Extension methods |
| 950 |
|
|
| 951 |
|
/** |
| 952 |
< |
* Returns the result that would be returned by {@code join}, |
| 953 |
< |
* even if this task completed abnormally, or null if this task is |
| 954 |
< |
* not known to have been completed. This method is designed to |
| 955 |
< |
* aid debugging, as well as to support extensions. Its use in any |
| 956 |
< |
* other context is discouraged. |
| 952 |
> |
* Returns the result that would be returned by {@link #join}, even |
| 953 |
> |
* if this task completed abnormally, or {@code null} if this task |
| 954 |
> |
* is not known to have been completed. This method is designed |
| 955 |
> |
* to aid debugging, as well as to support extensions. Its use in |
| 956 |
> |
* any other context is discouraged. |
| 957 |
|
* |
| 958 |
< |
* @return the result, or null if not completed |
| 958 |
> |
* @return the result, or {@code null} if not completed |
| 959 |
|
*/ |
| 960 |
|
public abstract V getRawResult(); |
| 961 |
|
|
| 974 |
|
* called otherwise. The return value controls whether this task |
| 975 |
|
* is considered to be done normally. It may return false in |
| 976 |
|
* asynchronous actions that require explicit invocations of |
| 977 |
< |
* {@code complete} to become joinable. It may throw exceptions |
| 977 |
> |
* {@link #complete} to become joinable. It may throw exceptions |
| 978 |
|
* to indicate abnormal exit. |
| 979 |
|
* |
| 980 |
< |
* @return true if completed normally |
| 980 |
> |
* @return {@code true} if completed normally |
| 981 |
|
* @throws Error or RuntimeException if encountered during computation |
| 982 |
|
*/ |
| 983 |
|
protected abstract boolean exec(); |
| 993 |
|
* #inForkJoinPool}). Attempts to invoke in other contexts result |
| 994 |
|
* in exceptions or errors, possibly including ClassCastException. |
| 995 |
|
* |
| 996 |
< |
* @return the next task, or null if none are available |
| 996 |
> |
* @return the next task, or {@code null} if none are available |
| 997 |
|
*/ |
| 998 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
| 999 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
| 1010 |
|
* contexts result in exceptions or errors, possibly including |
| 1011 |
|
* ClassCastException. |
| 1012 |
|
* |
| 1013 |
< |
* @return the next task, or null if none are available |
| 1013 |
> |
* @return the next task, or {@code null} if none are available |
| 1014 |
|
*/ |
| 1015 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
| 1016 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
| 1031 |
|
* result in exceptions or errors, possibly including |
| 1032 |
|
* ClassCastException. |
| 1033 |
|
* |
| 1034 |
< |
* @return a task, or null if none are available |
| 1034 |
> |
* @return a task, or {@code null} if none are available |
| 1035 |
|
*/ |
| 1036 |
|
protected static ForkJoinTask<?> pollTask() { |
| 1037 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
| 1086 |
|
* Save the state to a stream. |
| 1087 |
|
* |
| 1088 |
|
* @serialData the current run status and the exception thrown |
| 1089 |
< |
* during execution, or null if none |
| 1089 |
> |
* during execution, or {@code null} if none |
| 1090 |
|
* @param s the stream |
| 1091 |
|
*/ |
| 1092 |
|
private void writeObject(java.io.ObjectOutputStream s) |
