| 76 |
|
* |
| 77 |
|
* <p> The ForkJoinTask class is not usually directly subclassed. |
| 78 |
|
* Instead, you subclass one of the abstract classes that support a |
| 79 |
< |
* particular style of fork/join processing. Normally, a concrete |
| 79 |
> |
* particular style of fork/join processing, typically {@link |
| 80 |
> |
* RecursiveAction} for computations that do not return results, or |
| 81 |
> |
* {@link RecursiveTask} for those that do. Normally, a concrete |
| 82 |
|
* ForkJoinTask subclass declares fields comprising its parameters, |
| 83 |
|
* established in a constructor, and then defines a {@code compute} |
| 84 |
|
* method that somehow uses the control methods supplied by this base |
| 108 |
|
* parallelism cannot improve throughput. If too small, then memory |
| 109 |
|
* and internal task maintenance overhead may overwhelm processing. |
| 110 |
|
* |
| 111 |
+ |
* <p>This class provides {@code adapt} methods for {@link |
| 112 |
+ |
* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
| 113 |
+ |
* may be of use when mixing execution of ForkJoinTasks with other |
| 114 |
+ |
* kinds of tasks. When all tasks are of this form, consider using a |
| 115 |
+ |
* pool in {@link ForkJoinPool#setAsyncMode}. |
| 116 |
+ |
* |
| 117 |
|
* <p>ForkJoinTasks are {@code Serializable}, which enables them |
| 118 |
|
* to be used in extensions such as remote execution frameworks. It is |
| 119 |
|
* in general sensible to serialize tasks only before or after, but |
| 539 |
|
} |
| 540 |
|
|
| 541 |
|
/** |
| 542 |
< |
* Forks both tasks, returning when {@code isDone} holds for |
| 543 |
< |
* both of them or an exception is encountered. This method may be |
| 542 |
> |
* Forks the given tasks, returning when {@code isDone} holds for |
| 543 |
> |
* each task or an exception is encountered. This method may be |
| 544 |
|
* invoked only from within ForkJoinTask computations (as may be |
| 545 |
|
* determined using method {@link #inForkJoinPool}). Attempts to |
| 546 |
|
* invoke in other contexts result in exceptions or errors, |
| 547 |
|
* possibly including ClassCastException. |
| 548 |
|
* |
| 549 |
< |
* @param t1 one task |
| 550 |
< |
* @param t2 the other task |
| 551 |
< |
* @throws NullPointerException if t1 or t2 are null |
| 552 |
< |
* @throws RuntimeException or Error if either task did so |
| 549 |
> |
* @param t1 the first task |
| 550 |
> |
* @param t2 the second task |
| 551 |
> |
* @throws NullPointerException if any task is null |
| 552 |
> |
* @throws RuntimeException or Error if a task did so |
| 553 |
|
*/ |
| 554 |
|
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
| 555 |
|
t2.fork(); |
| 558 |
|
} |
| 559 |
|
|
| 560 |
|
/** |
| 561 |
< |
* Forks the given tasks, returning when {@code isDone} holds |
| 562 |
< |
* for all of them. If any task encounters an exception, others |
| 563 |
< |
* may be cancelled. This method may be invoked only from within |
| 561 |
> |
* Forks the given tasks, returning when {@code isDone} holds for |
| 562 |
> |
* each task or an exception is encountered. If any task |
| 563 |
> |
* encounters an exception, others may be, but are not guaranteed |
| 564 |
> |
* to be, cancelled. This method may be invoked only from within |
| 565 |
|
* ForkJoinTask computations (as may be determined using method |
| 566 |
|
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 567 |
|
* result in exceptions or errors, possibly including |
| 568 |
|
* ClassCastException. |
| 569 |
|
* |
| 570 |
< |
* @param tasks the array of tasks |
| 570 |
> |
* Overloadings of this method exist for the special cases |
| 571 |
> |
* of one to four arguments. |
| 572 |
> |
* |
| 573 |
> |
* @param tasks the tasks |
| 574 |
|
* @throws NullPointerException if tasks or any element are null |
| 575 |
|
* @throws RuntimeException or Error if any task did so |
| 576 |
|
*/ |
| 608 |
|
} |
| 609 |
|
|
| 610 |
|
/** |
| 611 |
< |
* Forks all tasks in the collection, returning when |
| 612 |
< |
* {@code isDone} holds for all of them. If any task |
| 613 |
< |
* encounters an exception, others may be cancelled. This method |
| 614 |
< |
* may be invoked only from within ForkJoinTask computations (as |
| 615 |
< |
* may be determined using method {@link |
| 616 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
| 617 |
< |
* in exceptions or errors, possibly including ClassCastException. |
| 611 |
> |
* Forks all tasks in the collection, returning when {@code |
| 612 |
> |
* isDone} holds for each task or an exception is encountered. If |
| 613 |
> |
* any task encounters an exception, others may be, but are not |
| 614 |
> |
* guaranteed to be, cancelled. This method may be invoked only |
| 615 |
> |
* from within ForkJoinTask computations (as may be determined |
| 616 |
> |
* using method {@link #inForkJoinPool}). Attempts to invoke in |
| 617 |
> |
* other contexts result in exceptions or errors, possibly |
| 618 |
> |
* including ClassCastException. |
| 619 |
|
* |
| 620 |
|
* @param tasks the collection of tasks |
| 621 |
|
* @return the tasks argument, to simplify usage |
| 745 |
|
* {@code join} and related operations. This method may be used |
| 746 |
|
* to induce exceptions in asynchronous tasks, or to force |
| 747 |
|
* completion of tasks that would not otherwise complete. Its use |
| 748 |
< |
* in other situations is likely to be wrong. This method is |
| 748 |
> |
* in other situations is discouraged. This method is |
| 749 |
|
* overridable, but overridden versions must invoke {@code super} |
| 750 |
|
* implementation to maintain guarantees. |
| 751 |
|
* |
| 765 |
|
* operations. This method may be used to provide results for |
| 766 |
|
* asynchronous tasks, or to provide alternative handling for |
| 767 |
|
* tasks that would not otherwise complete normally. Its use in |
| 768 |
< |
* other situations is likely to be wrong. This method is |
| 768 |
> |
* other situations is discouraged. This method is |
| 769 |
|
* overridable, but overridden versions must invoke {@code super} |
| 770 |
|
* implementation to maintain guarantees. |
| 771 |
|
* |
| 865 |
|
* Possibly executes tasks until the pool hosting the current task |
| 866 |
|
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
| 867 |
|
* designs in which many tasks are forked, but none are explicitly |
| 868 |
< |
* joined, instead executing them until all are processed. |
| 868 |
> |
* joined, instead executing them until all are processed. This |
| 869 |
> |
* method may be invoked only from within ForkJoinTask |
| 870 |
> |
* computations (as may be determined using method {@link |
| 871 |
> |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
| 872 |
> |
* in exceptions or errors, possibly including ClassCastException. |
| 873 |
|
*/ |
| 874 |
|
public static void helpQuiesce() { |
| 875 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
| 883 |
|
* never been forked, or has been forked, then completed and all |
| 884 |
|
* outstanding joins of this task have also completed. Effects |
| 885 |
|
* under any other usage conditions are not guaranteed, and are |
| 886 |
< |
* almost surely wrong. This method may be useful when executing |
| 886 |
> |
* discouraged. This method may be useful when executing |
| 887 |
|
* pre-constructed trees of subtasks in loops. |
| 888 |
|
*/ |
| 889 |
|
public void reinitialize() { |
| 896 |
|
* Returns the pool hosting the current task execution, or null |
| 897 |
|
* if this task is executing outside of any ForkJoinPool. |
| 898 |
|
* |
| 899 |
+ |
* @see #inForkJoinPool |
| 900 |
|
* @return the pool, or {@code null} if none |
| 901 |
|
*/ |
| 902 |
|
public static ForkJoinPool getPool() { |
| 939 |
|
* Returns an estimate of the number of tasks that have been |
| 940 |
|
* forked by the current worker thread but not yet executed. This |
| 941 |
|
* value may be useful for heuristic decisions about whether to |
| 942 |
< |
* fork other tasks. |
| 943 |
< |
* |
| 942 |
> |
* fork other tasks. This method may be invoked only from within |
| 943 |
> |
* ForkJoinTask computations (as may be determined using method |
| 944 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 945 |
> |
* result in exceptions or errors, possibly including |
| 946 |
> |
* ClassCastException. |
| 947 |
|
* @return the number of tasks |
| 948 |
|
*/ |
| 949 |
|
public static int getQueuedTaskCount() { |
| 959 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
| 960 |
|
* aim to maintain a small constant surplus (for example, 3) of |
| 961 |
|
* tasks, and to process computations locally if this threshold is |
| 962 |
< |
* exceeded. |
| 963 |
< |
* |
| 962 |
> |
* exceeded. This method may be invoked only from within |
| 963 |
> |
* ForkJoinTask computations (as may be determined using method |
| 964 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 965 |
> |
* result in exceptions or errors, possibly including |
| 966 |
> |
* ClassCastException. * |
| 967 |
|
* @return the surplus number of tasks, which may be negative |
| 968 |
|
*/ |
| 969 |
|
public static int getSurplusQueuedTaskCount() { |
| 1097 |
|
*/ |
| 1098 |
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
| 1099 |
|
implements RunnableFuture<T> { |
| 1100 |
< |
final Callable<T> callable; |
| 1100 |
> |
final Callable<? extends T> callable; |
| 1101 |
|
T result; |
| 1102 |
< |
AdaptedCallable(Callable<T> callable) { |
| 1102 |
> |
AdaptedCallable(Callable<? extends T> callable) { |
| 1103 |
|
if (callable == null) throw new NullPointerException(); |
| 1104 |
|
this.callable = callable; |
| 1105 |
|
} |
| 1129 |
|
* @param runnable the runnable action |
| 1130 |
|
* @return the task |
| 1131 |
|
*/ |
| 1132 |
< |
public static ForkJoinTask<Void> adapt(Runnable runnable) { |
| 1132 |
> |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
| 1133 |
|
return new AdaptedRunnable<Void>(runnable, null); |
| 1134 |
|
} |
| 1135 |
|
|
| 1155 |
|
* @param callable the callable action |
| 1156 |
|
* @return the task |
| 1157 |
|
*/ |
| 1158 |
< |
public static <T> ForkJoinTask<T> adapt(Callable<T> callable) { |
| 1158 |
> |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
| 1159 |
|
return new AdaptedCallable<T>(callable); |
| 1160 |
|
} |
| 1161 |
|
|
