16 |
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import java.util.WeakHashMap; |
17 |
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18 |
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/** |
19 |
< |
* Abstract base class for tasks that run within a {@link |
20 |
< |
* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much |
19 |
> |
* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
20 |
> |
* A {@code ForkJoinTask} is a thread-like entity that is much |
21 |
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* lighter weight than a normal thread. Huge numbers of tasks and |
22 |
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* subtasks may be hosted by a small number of actual threads in a |
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* ForkJoinPool, at the price of some usage limitations. |
25 |
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* <p> A "main" ForkJoinTask begins execution when submitted to a |
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* {@link ForkJoinPool}. Once started, it will usually in turn start |
27 |
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* other subtasks. As indicated by the name of this class, many |
28 |
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* programs using ForkJoinTasks employ only methods {@code fork} |
29 |
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* and {@code join}, or derivatives such as |
30 |
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* {@code invokeAll}. However, this class also provides a number |
31 |
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* 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 |
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* fork/join processing. |
28 |
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* programs using ForkJoinTasks employ only methods {@code fork} and |
29 |
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* {@code join}, or derivatives such as {@code invokeAll}. However, |
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* 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. |
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* |
34 |
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* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
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* efficiency of ForkJoinTasks stems from a set of restrictions (that |
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* lightweight task scheduling framework, and so cannot be overridden. |
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* Developers creating new basic styles of fork/join processing should |
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* minimally implement {@code protected} methods |
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* {@code exec}, {@code setRawResult}, and |
97 |
< |
* {@code getRawResult}, while also introducing an abstract |
96 |
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* {@link #exec}, {@link #setRawResult}, and |
97 |
> |
* {@link #getRawResult}, while also introducing an abstract |
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* computational method that can be implemented in its subclasses, |
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* possibly relying on other {@code protected} methods provided |
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* by this class. |
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synchronized (this) { |
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try { |
249 |
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while (status >= 0) { |
250 |
< |
long nt = nanos - System.nanoTime() - startTime; |
250 |
> |
long nt = nanos - (System.nanoTime() - startTime); |
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if (nt <= 0) |
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break; |
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wait(nt / 1000000, (int) (nt % 1000000)); |
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} |
652 |
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|
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/** |
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 |
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* |
657 |
< |
* @return true if this computation has completed |
657 |
> |
* @return {@code true} if this computation has completed |
658 |
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*/ |
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public final boolean isDone() { |
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return status < 0; |
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} |
662 |
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|
663 |
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/** |
664 |
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* Returns true if this task was cancelled. |
664 |
> |
* Returns {@code true} if this task was cancelled. |
665 |
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* |
666 |
< |
* @return true if this task was cancelled |
666 |
> |
* @return {@code true} if this task was cancelled |
667 |
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*/ |
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public final boolean isCancelled() { |
669 |
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return (status & COMPLETION_MASK) == CANCELLED; |
672 |
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/** |
673 |
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* Asserts that the results of this task's computation will not be |
674 |
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* used. If a cancellation occurs before attempting to execute this |
675 |
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* 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 |
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* {@code CancellationException} being thrown. Otherwise, when |
678 |
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* 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 |
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* invocation. |
683 |
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* |
684 |
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* <p>This method may be overridden in subclasses, but if so, must |
688 |
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* <p> This method is designed to be invoked by <em>other</em> |
689 |
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* tasks. To terminate the current task, you can just return or |
690 |
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* throw an unchecked exception from its computation method, or |
691 |
< |
* invoke {@code completeExceptionally}. |
691 |
> |
* invoke {@link #completeExceptionally}. |
692 |
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* |
693 |
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* @param mayInterruptIfRunning this value is ignored in the |
694 |
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* default implementation because tasks are not in general |
695 |
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* cancelled via interruption |
696 |
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* |
697 |
< |
* @return true if this task is now cancelled |
697 |
> |
* @return {@code true} if this task is now cancelled |
698 |
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*/ |
699 |
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public boolean cancel(boolean mayInterruptIfRunning) { |
700 |
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setCompletion(CANCELLED); |
702 |
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} |
703 |
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|
704 |
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/** |
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 |
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* |
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 |
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*/ |
709 |
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public final boolean isCompletedAbnormally() { |
710 |
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return (status & COMPLETION_MASK) < NORMAL; |
715 |
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* CancellationException if cancelled, or null if none or if the |
716 |
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* method has not yet completed. |
717 |
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* |
718 |
< |
* @return the exception, or null if none |
718 |
> |
* @return the exception, or {@code null} if none |
719 |
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*/ |
720 |
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public final Throwable getException() { |
721 |
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int s = status & COMPLETION_MASK; |
777 |
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|
778 |
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public final V get(long timeout, TimeUnit unit) |
779 |
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throws InterruptedException, ExecutionException, TimeoutException { |
780 |
+ |
long nanos = unit.toNanos(timeout); |
781 |
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ForkJoinWorkerThread w = getWorker(); |
782 |
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if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
783 |
< |
awaitDone(w, unit.toNanos(timeout)); |
783 |
> |
awaitDone(w, nanos); |
784 |
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return reportTimedFutureResult(); |
785 |
|
} |
786 |
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|
879 |
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* Returns the pool hosting the current task execution, or null |
880 |
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* if this task is executing outside of any ForkJoinPool. |
881 |
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* |
882 |
< |
* @return the pool, or null if none |
882 |
> |
* @return the pool, or {@code null} if none |
883 |
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*/ |
884 |
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public static ForkJoinPool getPool() { |
885 |
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Thread t = Thread.currentThread(); |
910 |
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* result in exceptions or errors, possibly including |
911 |
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* ClassCastException. |
912 |
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* |
913 |
< |
* @return true if unforked |
913 |
> |
* @return {@code true} if unforked |
914 |
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*/ |
915 |
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public boolean tryUnfork() { |
916 |
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return ((ForkJoinWorkerThread) Thread.currentThread()) |
950 |
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// Extension methods |
951 |
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|
952 |
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/** |
953 |
< |
* Returns the result that would be returned by {@code join}, |
954 |
< |
* even if this task completed abnormally, or null if this task is |
955 |
< |
* not known to have been completed. This method is designed to |
956 |
< |
* aid debugging, as well as to support extensions. Its use in any |
957 |
< |
* other context is discouraged. |
953 |
> |
* Returns the result that would be returned by {@link #join}, even |
954 |
> |
* if this task completed abnormally, or {@code null} if this task |
955 |
> |
* is not known to have been completed. This method is designed |
956 |
> |
* to aid debugging, as well as to support extensions. Its use in |
957 |
> |
* any other context is discouraged. |
958 |
|
* |
959 |
< |
* @return the result, or null if not completed |
959 |
> |
* @return the result, or {@code null} if not completed |
960 |
|
*/ |
961 |
|
public abstract V getRawResult(); |
962 |
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|
975 |
|
* called otherwise. The return value controls whether this task |
976 |
|
* is considered to be done normally. It may return false in |
977 |
|
* asynchronous actions that require explicit invocations of |
978 |
< |
* {@code complete} to become joinable. It may throw exceptions |
978 |
> |
* {@link #complete} to become joinable. It may throw exceptions |
979 |
|
* to indicate abnormal exit. |
980 |
|
* |
981 |
< |
* @return true if completed normally |
981 |
> |
* @return {@code true} if completed normally |
982 |
|
* @throws Error or RuntimeException if encountered during computation |
983 |
|
*/ |
984 |
|
protected abstract boolean exec(); |
985 |
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|
986 |
|
/** |
987 |
< |
* Returns, but does not unschedule or execute, the task queued by |
988 |
< |
* the current thread but not yet executed, if one is |
987 |
> |
* Returns, but does not unschedule or execute, a task queued by |
988 |
> |
* the current thread but not yet executed, if one is immediately |
989 |
|
* available. There is no guarantee that this task will actually |
990 |
< |
* be polled or executed next. This method is designed primarily |
991 |
< |
* to support extensions, and is unlikely to be useful otherwise. |
992 |
< |
* This method may be invoked only from within ForkJoinTask |
993 |
< |
* computations (as may be determined using method {@link |
994 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
995 |
< |
* in exceptions or errors, possibly including ClassCastException. |
990 |
> |
* be polled or executed next. Conversely, this method may return |
991 |
> |
* null even if a task exists but cannot be accessed without |
992 |
> |
* contention with other threads. This method is designed |
993 |
> |
* primarily to support extensions, and is unlikely to be useful |
994 |
> |
* otherwise. This method may be invoked only from within |
995 |
> |
* ForkJoinTask computations (as may be determined using method |
996 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
997 |
> |
* result in exceptions or errors, possibly including |
998 |
> |
* ClassCastException. |
999 |
|
* |
1000 |
< |
* @return the next task, or null if none are available |
1000 |
> |
* @return the next task, or {@code null} if none are available |
1001 |
|
*/ |
1002 |
|
protected static ForkJoinTask<?> peekNextLocalTask() { |
1003 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1014 |
|
* contexts result in exceptions or errors, possibly including |
1015 |
|
* ClassCastException. |
1016 |
|
* |
1017 |
< |
* @return the next task, or null if none are available |
1017 |
> |
* @return the next task, or {@code null} if none are available |
1018 |
|
*/ |
1019 |
|
protected static ForkJoinTask<?> pollNextLocalTask() { |
1020 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1035 |
|
* result in exceptions or errors, possibly including |
1036 |
|
* ClassCastException. |
1037 |
|
* |
1038 |
< |
* @return a task, or null if none are available |
1038 |
> |
* @return a task, or {@code null} if none are available |
1039 |
|
*/ |
1040 |
|
protected static ForkJoinTask<?> pollTask() { |
1041 |
|
return ((ForkJoinWorkerThread) Thread.currentThread()) |
1042 |
|
.pollTask(); |
1043 |
|
} |
1044 |
|
|
1045 |
< |
// adaptors |
1045 |
> |
/** |
1046 |
> |
* Adaptor for Runnables. This implements RunnableFuture |
1047 |
> |
* to be compliant with AbstractExecutorService constraints |
1048 |
> |
* when used in ForkJoinPool. |
1049 |
> |
*/ |
1050 |
> |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
1051 |
> |
implements RunnableFuture<T> { |
1052 |
> |
final Runnable runnable; |
1053 |
> |
final T resultOnCompletion; |
1054 |
> |
T result; |
1055 |
> |
AdaptedRunnable(Runnable runnable, T result) { |
1056 |
> |
if (runnable == null) throw new NullPointerException(); |
1057 |
> |
this.runnable = runnable; |
1058 |
> |
this.resultOnCompletion = result; |
1059 |
> |
} |
1060 |
> |
public T getRawResult() { return result; } |
1061 |
> |
public void setRawResult(T v) { result = v; } |
1062 |
> |
public boolean exec() { |
1063 |
> |
runnable.run(); |
1064 |
> |
result = resultOnCompletion; |
1065 |
> |
return true; |
1066 |
> |
} |
1067 |
> |
public void run() { invoke(); } |
1068 |
> |
private static final long serialVersionUID = 5232453952276885070L; |
1069 |
> |
} |
1070 |
> |
|
1071 |
> |
/** |
1072 |
> |
* Adaptor for Callables |
1073 |
> |
*/ |
1074 |
> |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
1075 |
> |
implements RunnableFuture<T> { |
1076 |
> |
final Callable<T> callable; |
1077 |
> |
T result; |
1078 |
> |
AdaptedCallable(Callable<T> callable) { |
1079 |
> |
if (callable == null) throw new NullPointerException(); |
1080 |
> |
this.callable = callable; |
1081 |
> |
} |
1082 |
> |
public T getRawResult() { return result; } |
1083 |
> |
public void setRawResult(T v) { result = v; } |
1084 |
> |
public boolean exec() { |
1085 |
> |
try { |
1086 |
> |
result = callable.call(); |
1087 |
> |
return true; |
1088 |
> |
} catch (Error err) { |
1089 |
> |
throw err; |
1090 |
> |
} catch (RuntimeException rex) { |
1091 |
> |
throw rex; |
1092 |
> |
} catch (Exception ex) { |
1093 |
> |
throw new RuntimeException(ex); |
1094 |
> |
} |
1095 |
> |
} |
1096 |
> |
public void run() { invoke(); } |
1097 |
> |
private static final long serialVersionUID = 2838392045355241008L; |
1098 |
> |
} |
1099 |
|
|
1100 |
|
/** |
1101 |
|
* Returns a new ForkJoinTask that performs the {@code run} |
1106 |
|
* @return the task |
1107 |
|
*/ |
1108 |
|
public static ForkJoinTask<Void> adapt(Runnable runnable) { |
1109 |
< |
return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null); |
1109 |
> |
return new AdaptedRunnable<Void>(runnable, null); |
1110 |
|
} |
1111 |
|
|
1112 |
|
/** |
1119 |
|
* @return the task |
1120 |
|
*/ |
1121 |
|
public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) { |
1122 |
< |
return new ForkJoinPool.AdaptedRunnable<T>(runnable, result); |
1122 |
> |
return new AdaptedRunnable<T>(runnable, result); |
1123 |
|
} |
1124 |
|
|
1125 |
|
/** |
1132 |
|
* @return the task |
1133 |
|
*/ |
1134 |
|
public static <T> ForkJoinTask<T> adapt(Callable<T> callable) { |
1135 |
< |
return new ForkJoinPool.AdaptedCallable<T>(callable); |
1135 |
> |
return new AdaptedCallable<T>(callable); |
1136 |
|
} |
1137 |
|
|
1138 |
|
// Serialization support |
1143 |
|
* Save the state to a stream. |
1144 |
|
* |
1145 |
|
* @serialData the current run status and the exception thrown |
1146 |
< |
* during execution, or null if none |
1146 |
> |
* during execution, or {@code null} if none |
1147 |
|
* @param s the stream |
1148 |
|
*/ |
1149 |
|
private void writeObject(java.io.ObjectOutputStream s) |