| 14 |
|
import java.util.WeakHashMap; |
| 15 |
|
|
| 16 |
|
/** |
| 17 |
< |
* Abstract base class for tasks that run within a {@link |
| 18 |
< |
* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much |
| 17 |
> |
* Abstract base class for tasks that run within a {@link ForkJoinPool}. |
| 18 |
> |
* A {@code ForkJoinTask} is a thread-like entity that is much |
| 19 |
|
* lighter weight than a normal thread. Huge numbers of tasks and |
| 20 |
|
* subtasks may be hosted by a small number of actual threads in a |
| 21 |
|
* ForkJoinPool, at the price of some usage limitations. |
| 22 |
|
* |
| 23 |
< |
* <p> A "main" ForkJoinTask begins execution when submitted to a |
| 24 |
< |
* {@link ForkJoinPool}. Once started, it will usually in turn start |
| 25 |
< |
* other subtasks. As indicated by the name of this class, many |
| 26 |
< |
* programs using ForkJoinTasks employ only methods {@code fork} and |
| 27 |
< |
* {@code join}, or derivatives such as {@code invokeAll}. However, |
| 28 |
< |
* this class also provides a number of other methods that can come |
| 29 |
< |
* into play in advanced usages, as well as extension mechanics that |
| 30 |
< |
* allow support of new forms of fork/join processing. |
| 23 |
> |
* <p>A "main" {@code ForkJoinTask} begins execution when submitted |
| 24 |
> |
* to a {@link ForkJoinPool}. Once started, it will usually in turn |
| 25 |
> |
* start other subtasks. As indicated by the name of this class, |
| 26 |
> |
* many programs using {@code ForkJoinTask} employ only methods |
| 27 |
> |
* {@link #fork} and {@link #join}, or derivatives such as {@link |
| 28 |
> |
* #invokeAll}. However, this class also provides a number of other |
| 29 |
> |
* methods that can come into play in advanced usages, as well as |
| 30 |
> |
* extension mechanics that allow support of new forms of fork/join |
| 31 |
> |
* processing. |
| 32 |
|
* |
| 33 |
< |
* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
| 34 |
< |
* efficiency of ForkJoinTasks stems from a set of restrictions (that |
| 35 |
< |
* are only partially statically enforceable) reflecting their |
| 36 |
< |
* intended use as computational tasks calculating pure functions or |
| 37 |
< |
* operating on purely isolated objects. The primary coordination |
| 38 |
< |
* mechanisms are {@link #fork}, that arranges asynchronous execution, |
| 39 |
< |
* and {@link #join}, that doesn't proceed until the task's result has |
| 40 |
< |
* been computed. Computations should avoid {@code synchronized} |
| 41 |
< |
* methods or blocks, and should minimize other blocking |
| 42 |
< |
* synchronization apart from joining other tasks or using |
| 43 |
< |
* synchronizers such as Phasers that are advertised to cooperate with |
| 44 |
< |
* fork/join scheduling. Tasks should also not perform blocking IO, |
| 45 |
< |
* and should ideally access variables that are completely independent |
| 46 |
< |
* of those accessed by other running tasks. Minor breaches of these |
| 47 |
< |
* restrictions, for example using shared output streams, may be |
| 48 |
< |
* tolerable in practice, but frequent use may result in poor |
| 49 |
< |
* performance, and the potential to indefinitely stall if the number |
| 50 |
< |
* of threads not waiting for IO or other external synchronization |
| 51 |
< |
* becomes exhausted. This usage restriction is in part enforced by |
| 52 |
< |
* not permitting checked exceptions such as {@code IOExceptions} |
| 53 |
< |
* to be thrown. However, computations may still encounter unchecked |
| 54 |
< |
* exceptions, that are rethrown to callers attempting join |
| 55 |
< |
* them. These exceptions may additionally include |
| 56 |
< |
* RejectedExecutionExceptions stemming from internal resource |
| 57 |
< |
* exhaustion such as failure to allocate internal task queues. |
| 33 |
> |
* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}. |
| 34 |
> |
* The efficiency of {@code ForkJoinTask}s stems from a set of |
| 35 |
> |
* restrictions (that are only partially statically enforceable) |
| 36 |
> |
* reflecting their intended use as computational tasks calculating |
| 37 |
> |
* pure functions or operating on purely isolated objects. The |
| 38 |
> |
* primary coordination mechanisms are {@link #fork}, that arranges |
| 39 |
> |
* asynchronous execution, and {@link #join}, that doesn't proceed |
| 40 |
> |
* until the task's result has been computed. Computations should |
| 41 |
> |
* avoid {@code synchronized} methods or blocks, and should minimize |
| 42 |
> |
* other blocking synchronization apart from joining other tasks or |
| 43 |
> |
* using synchronizers such as Phasers that are advertised to |
| 44 |
> |
* cooperate with fork/join scheduling. Tasks should also not perform |
| 45 |
> |
* blocking IO, and should ideally access variables that are |
| 46 |
> |
* completely independent of those accessed by other running |
| 47 |
> |
* tasks. Minor breaches of these restrictions, for example using |
| 48 |
> |
* shared output streams, may be tolerable in practice, but frequent |
| 49 |
> |
* use may result in poor performance, and the potential to |
| 50 |
> |
* indefinitely stall if the number of threads not waiting for IO or |
| 51 |
> |
* other external synchronization becomes exhausted. This usage |
| 52 |
> |
* restriction is in part enforced by not permitting checked |
| 53 |
> |
* exceptions such as {@code IOExceptions} to be thrown. However, |
| 54 |
> |
* computations may still encounter unchecked exceptions, that are |
| 55 |
> |
* rethrown to callers attempting join them. These exceptions may |
| 56 |
> |
* additionally include RejectedExecutionExceptions stemming from |
| 57 |
> |
* internal resource exhaustion such as failure to allocate internal |
| 58 |
> |
* task queues. |
| 59 |
|
* |
| 60 |
|
* <p>The primary method for awaiting completion and extracting |
| 61 |
|
* results of a task is {@link #join}, but there are several variants: |
| 74 |
|
* performs the most common form of parallel invocation: forking a set |
| 75 |
|
* of tasks and joining them all. |
| 76 |
|
* |
| 77 |
< |
* <p> The ForkJoinTask class is not usually directly subclassed. |
| 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 |
| 494 |
|
/** |
| 495 |
|
* Arranges to asynchronously execute this task. While it is not |
| 496 |
|
* necessarily enforced, it is a usage error to fork a task more |
| 497 |
< |
* than once unless it has completed and been reinitialized. This |
| 498 |
< |
* method may be invoked only from within ForkJoinTask |
| 499 |
< |
* computations (as may be determined using method {@link |
| 500 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
| 501 |
< |
* in exceptions or errors, possibly including ClassCastException. |
| 497 |
> |
* than once unless it has completed and been reinitialized. |
| 498 |
> |
* |
| 499 |
> |
* <p>This method may be invoked only from within {@code |
| 500 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 501 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 502 |
> |
* result in exceptions or errors, possibly including {@code |
| 503 |
> |
* ClassCastException}. |
| 504 |
|
* |
| 505 |
< |
* @return {@code this}, to simplify usage. |
| 505 |
> |
* @return {@code this}, to simplify usage |
| 506 |
|
*/ |
| 507 |
|
public final ForkJoinTask<V> fork() { |
| 508 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
| 512 |
|
|
| 513 |
|
/** |
| 514 |
|
* Returns the result of the computation when it is ready. |
| 515 |
< |
* This method differs from {@code get} in that abnormal |
| 516 |
< |
* completion results in RuntimeExceptions or Errors, not |
| 517 |
< |
* ExecutionExceptions. |
| 515 |
> |
* This method differs from {@link #get()} in that |
| 516 |
> |
* abnormal completion results in {@code RuntimeException} or |
| 517 |
> |
* {@code Error}, not {@code ExecutionException}. |
| 518 |
|
* |
| 519 |
|
* @return the computed result |
| 520 |
|
*/ |
| 541 |
|
} |
| 542 |
|
|
| 543 |
|
/** |
| 544 |
< |
* Forks both tasks, returning when {@code isDone} holds for |
| 545 |
< |
* both of them or an exception is encountered. This method may be |
| 546 |
< |
* invoked only from within ForkJoinTask computations (as may be |
| 547 |
< |
* determined using method {@link #inForkJoinPool}). Attempts to |
| 548 |
< |
* invoke in other contexts result in exceptions or errors, |
| 549 |
< |
* possibly including ClassCastException. |
| 550 |
< |
* |
| 551 |
< |
* @param t1 one task |
| 552 |
< |
* @param t2 the other task |
| 553 |
< |
* @throws NullPointerException if t1 or t2 are null |
| 554 |
< |
* @throws RuntimeException or Error if either task did so |
| 544 |
> |
* Forks the given tasks, returning when {@code isDone} holds |
| 545 |
> |
* for each task or an exception is encountered. |
| 546 |
> |
* |
| 547 |
> |
* <p>This method may be invoked only from within {@code |
| 548 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 549 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 550 |
> |
* result in exceptions or errors, possibly including {@code |
| 551 |
> |
* ClassCastException}. |
| 552 |
> |
* |
| 553 |
> |
* @param t1 the first task |
| 554 |
> |
* @param t2 the second task |
| 555 |
> |
* @throws NullPointerException if any task is null |
| 556 |
> |
* @throws RuntimeException or Error if a task did so |
| 557 |
|
*/ |
| 558 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
| 558 |
> |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
| 559 |
|
t2.fork(); |
| 560 |
|
t1.invoke(); |
| 561 |
|
t2.join(); |
| 562 |
|
} |
| 563 |
|
|
| 564 |
|
/** |
| 565 |
< |
* Forks the given tasks, returning when {@code isDone} holds |
| 566 |
< |
* for all of them. If any task encounters an exception, others |
| 567 |
< |
* may be cancelled. This method may be invoked only from within |
| 568 |
< |
* ForkJoinTask computations (as may be determined using method |
| 569 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 570 |
< |
* result in exceptions or errors, possibly including |
| 571 |
< |
* ClassCastException. |
| 565 |
> |
* Forks the given tasks, returning when {@code isDone} holds for |
| 566 |
> |
* each task or an exception is encountered. If any task |
| 567 |
> |
* encounters an exception, others may be, but are not guaranteed |
| 568 |
> |
* to be, cancelled. |
| 569 |
> |
* |
| 570 |
> |
* <p>This method may be invoked only from within {@code |
| 571 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 572 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 573 |
> |
* result in exceptions or errors, possibly including {@code |
| 574 |
> |
* ClassCastException}. |
| 575 |
> |
* |
| 576 |
> |
* <p>Overloadings of this method exist for the special cases |
| 577 |
> |
* of one to four arguments. |
| 578 |
|
* |
| 579 |
< |
* @param tasks the array of tasks |
| 579 |
> |
* @param tasks the tasks |
| 580 |
|
* @throws NullPointerException if tasks or any element are null |
| 581 |
|
* @throws RuntimeException or Error if any task did so |
| 582 |
|
*/ |
| 614 |
|
} |
| 615 |
|
|
| 616 |
|
/** |
| 617 |
< |
* Forks all tasks in the collection, returning when |
| 618 |
< |
* {@code isDone} holds for all of them. If any task |
| 619 |
< |
* encounters an exception, others may be cancelled. This method |
| 620 |
< |
* may be invoked only from within ForkJoinTask computations (as |
| 621 |
< |
* may be determined using method {@link |
| 622 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
| 623 |
< |
* in exceptions or errors, possibly including ClassCastException. |
| 617 |
> |
* Forks all tasks in the collection, returning when {@code |
| 618 |
> |
* isDone} holds for each task or an exception is encountered. |
| 619 |
> |
* If any task encounters an exception, others may be, but are |
| 620 |
> |
* not guaranteed to be, cancelled. |
| 621 |
> |
* |
| 622 |
> |
* <p>This method may be invoked only from within {@code |
| 623 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 624 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 625 |
> |
* result in exceptions or errors, possibly including {@code |
| 626 |
> |
* ClassCastException}. |
| 627 |
|
* |
| 628 |
|
* @param tasks the collection of tasks |
| 629 |
|
* @return the tasks argument, to simplify usage |
| 704 |
|
* |
| 705 |
|
* <p>This method may be overridden in subclasses, but if so, must |
| 706 |
|
* still ensure that these minimal properties hold. In particular, |
| 707 |
< |
* the cancel method itself must not throw exceptions. |
| 707 |
> |
* the {@code cancel} method itself must not throw exceptions. |
| 708 |
|
* |
| 709 |
< |
* <p> This method is designed to be invoked by <em>other</em> |
| 709 |
> |
* <p>This method is designed to be invoked by <em>other</em> |
| 710 |
|
* tasks. To terminate the current task, you can just return or |
| 711 |
|
* throw an unchecked exception from its computation method, or |
| 712 |
|
* invoke {@link #completeExceptionally}. |
| 733 |
|
|
| 734 |
|
/** |
| 735 |
|
* Returns the exception thrown by the base computation, or a |
| 736 |
< |
* CancellationException if cancelled, or null if none or if the |
| 737 |
< |
* method has not yet completed. |
| 736 |
> |
* {@code CancellationException} if cancelled, or {@code null} if |
| 737 |
> |
* none or if the method has not yet completed. |
| 738 |
|
* |
| 739 |
|
* @return the exception, or {@code null} if none |
| 740 |
|
*/ |
| 753 |
|
* {@code join} and related operations. This method may be used |
| 754 |
|
* to induce exceptions in asynchronous tasks, or to force |
| 755 |
|
* completion of tasks that would not otherwise complete. Its use |
| 756 |
< |
* in other situations is likely to be wrong. This method is |
| 756 |
> |
* in other situations is discouraged. This method is |
| 757 |
|
* overridable, but overridden versions must invoke {@code super} |
| 758 |
|
* implementation to maintain guarantees. |
| 759 |
|
* |
| 773 |
|
* operations. This method may be used to provide results for |
| 774 |
|
* asynchronous tasks, or to provide alternative handling for |
| 775 |
|
* tasks that would not otherwise complete normally. Its use in |
| 776 |
< |
* other situations is likely to be wrong. This method is |
| 776 |
> |
* other situations is discouraged. This method is |
| 777 |
|
* overridable, but overridden versions must invoke {@code super} |
| 778 |
|
* implementation to maintain guarantees. |
| 779 |
|
* |
| 812 |
|
* there are no potential dependencies between continuation of the |
| 813 |
|
* current task and that of any other task that might be executed |
| 814 |
|
* while helping. (This usually holds for pure divide-and-conquer |
| 815 |
< |
* tasks). This method may be invoked only from within |
| 816 |
< |
* ForkJoinTask computations (as may be determined using method |
| 817 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 818 |
< |
* result in exceptions or errors, possibly including |
| 819 |
< |
* ClassCastException. |
| 815 |
> |
* tasks). |
| 816 |
> |
* |
| 817 |
> |
* <p>This method may be invoked only from within {@code |
| 818 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 819 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 820 |
> |
* result in exceptions or errors, possibly including {@code |
| 821 |
> |
* ClassCastException}. |
| 822 |
|
* |
| 823 |
|
* @return the computed result |
| 824 |
|
*/ |
| 830 |
|
} |
| 831 |
|
|
| 832 |
|
/** |
| 833 |
< |
* Possibly executes other tasks until this task is ready. This |
| 834 |
< |
* method may be invoked only from within ForkJoinTask |
| 835 |
< |
* computations (as may be determined using method {@link |
| 836 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
| 837 |
< |
* in exceptions or errors, possibly including ClassCastException. |
| 833 |
> |
* Possibly executes other tasks until this task is ready. |
| 834 |
> |
* |
| 835 |
> |
* <p>This method may be invoked only from within {@code |
| 836 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 837 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 838 |
> |
* result in exceptions or errors, possibly including {@code |
| 839 |
> |
* ClassCastException}. |
| 840 |
|
*/ |
| 841 |
|
public final void quietlyHelpJoin() { |
| 842 |
|
if (status >= 0) { |
| 878 |
|
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
| 879 |
|
* designs in which many tasks are forked, but none are explicitly |
| 880 |
|
* joined, instead executing them until all are processed. |
| 881 |
+ |
* |
| 882 |
+ |
* <p>This method may be invoked only from within {@code |
| 883 |
+ |
* ForkJoinTask} computations (as may be determined using method |
| 884 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 885 |
+ |
* result in exceptions or errors, possibly including {@code |
| 886 |
+ |
* ClassCastException}. |
| 887 |
|
*/ |
| 888 |
|
public static void helpQuiesce() { |
| 889 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
| 896 |
|
* this task, but only if reuse occurs when this task has either |
| 897 |
|
* never been forked, or has been forked, then completed and all |
| 898 |
|
* outstanding joins of this task have also completed. Effects |
| 899 |
< |
* under any other usage conditions are not guaranteed, and are |
| 900 |
< |
* almost surely wrong. This method may be useful when executing |
| 899 |
> |
* under any other usage conditions are not guaranteed. |
| 900 |
> |
* This method may be useful when executing |
| 901 |
|
* pre-constructed trees of subtasks in loops. |
| 902 |
|
*/ |
| 903 |
|
public void reinitialize() { |
| 910 |
|
* Returns the pool hosting the current task execution, or null |
| 911 |
|
* if this task is executing outside of any ForkJoinPool. |
| 912 |
|
* |
| 913 |
+ |
* @see #inForkJoinPool |
| 914 |
|
* @return the pool, or {@code null} if none |
| 915 |
|
*/ |
| 916 |
|
public static ForkJoinPool getPool() { |
| 936 |
|
* by the current thread, and has not commenced executing in |
| 937 |
|
* another thread. This method may be useful when arranging |
| 938 |
|
* alternative local processing of tasks that could have been, but |
| 939 |
< |
* were not, stolen. This method may be invoked only from within |
| 940 |
< |
* ForkJoinTask computations (as may be determined using method |
| 941 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 942 |
< |
* result in exceptions or errors, possibly including |
| 943 |
< |
* ClassCastException. |
| 939 |
> |
* were not, stolen. |
| 940 |
> |
* |
| 941 |
> |
* <p>This method may be invoked only from within {@code |
| 942 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 943 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 944 |
> |
* result in exceptions or errors, possibly including {@code |
| 945 |
> |
* ClassCastException}. |
| 946 |
|
* |
| 947 |
|
* @return {@code true} if unforked |
| 948 |
|
*/ |
| 957 |
|
* value may be useful for heuristic decisions about whether to |
| 958 |
|
* fork other tasks. |
| 959 |
|
* |
| 960 |
+ |
* <p>This method may be invoked only from within {@code |
| 961 |
+ |
* ForkJoinTask} computations (as may be determined using method |
| 962 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 963 |
+ |
* result in exceptions or errors, possibly including {@code |
| 964 |
+ |
* ClassCastException}. |
| 965 |
+ |
* |
| 966 |
|
* @return the number of tasks |
| 967 |
|
*/ |
| 968 |
|
public static int getQueuedTaskCount() { |
| 980 |
|
* tasks, and to process computations locally if this threshold is |
| 981 |
|
* exceeded. |
| 982 |
|
* |
| 983 |
+ |
* <p>This method may be invoked only from within {@code |
| 984 |
+ |
* ForkJoinTask} computations (as may be determined using method |
| 985 |
+ |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 986 |
+ |
* result in exceptions or errors, possibly including {@code |
| 987 |
+ |
* ClassCastException}. |
| 988 |
+ |
* |
| 989 |
|
* @return the surplus number of tasks, which may be negative |
| 990 |
|
*/ |
| 991 |
|
public static int getSurplusQueuedTaskCount() { |
| 1037 |
|
* null even if a task exists but cannot be accessed without |
| 1038 |
|
* contention with other threads. This method is designed |
| 1039 |
|
* primarily to support extensions, and is unlikely to be useful |
| 1040 |
< |
* otherwise. This method may be invoked only from within |
| 1041 |
< |
* ForkJoinTask computations (as may be determined using method |
| 1042 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 1043 |
< |
* result in exceptions or errors, possibly including |
| 1044 |
< |
* ClassCastException. |
| 1040 |
> |
* otherwise. |
| 1041 |
> |
* |
| 1042 |
> |
* <p>This method may be invoked only from within {@code |
| 1043 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 1044 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 1045 |
> |
* result in exceptions or errors, possibly including {@code |
| 1046 |
> |
* ClassCastException}. |
| 1047 |
|
* |
| 1048 |
|
* @return the next task, or {@code null} if none are available |
| 1049 |
|
*/ |
| 1056 |
|
* Unschedules and returns, without executing, the next task |
| 1057 |
|
* queued by the current thread but not yet executed. This method |
| 1058 |
|
* is designed primarily to support extensions, and is unlikely to |
| 1059 |
< |
* be useful otherwise. This method may be invoked only from |
| 1060 |
< |
* within ForkJoinTask computations (as may be determined using |
| 1061 |
< |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
| 1062 |
< |
* contexts result in exceptions or errors, possibly including |
| 1063 |
< |
* ClassCastException. |
| 1059 |
> |
* be useful otherwise. |
| 1060 |
> |
* |
| 1061 |
> |
* <p>This method may be invoked only from within {@code |
| 1062 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 1063 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 1064 |
> |
* result in exceptions or errors, possibly including {@code |
| 1065 |
> |
* ClassCastException}. |
| 1066 |
|
* |
| 1067 |
|
* @return the next task, or {@code null} if none are available |
| 1068 |
|
*/ |
| 1079 |
|
* {@code null} result does not necessarily imply quiescence |
| 1080 |
|
* of the pool this task is operating in. This method is designed |
| 1081 |
|
* primarily to support extensions, and is unlikely to be useful |
| 1082 |
< |
* otherwise. This method may be invoked only from within |
| 1083 |
< |
* ForkJoinTask computations (as may be determined using method |
| 1084 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 1085 |
< |
* result in exceptions or errors, possibly including |
| 1086 |
< |
* ClassCastException. |
| 1082 |
> |
* otherwise. |
| 1083 |
> |
* |
| 1084 |
> |
* <p>This method may be invoked only from within {@code |
| 1085 |
> |
* ForkJoinTask} computations (as may be determined using method |
| 1086 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
| 1087 |
> |
* result in exceptions or errors, possibly including {@code |
| 1088 |
> |
* ClassCastException}. |
| 1089 |
|
* |
| 1090 |
|
* @return a task, or {@code null} if none are available |
| 1091 |
|
*/ |
| 1125 |
|
*/ |
| 1126 |
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
| 1127 |
|
implements RunnableFuture<T> { |
| 1128 |
< |
final Callable<T> callable; |
| 1128 |
> |
final Callable<? extends T> callable; |
| 1129 |
|
T result; |
| 1130 |
< |
AdaptedCallable(Callable<T> callable) { |
| 1130 |
> |
AdaptedCallable(Callable<? extends T> callable) { |
| 1131 |
|
if (callable == null) throw new NullPointerException(); |
| 1132 |
|
this.callable = callable; |
| 1133 |
|
} |
| 1150 |
|
} |
| 1151 |
|
|
| 1152 |
|
/** |
| 1153 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
| 1154 |
< |
* method of the given Runnable as its action, and returns a null |
| 1155 |
< |
* result upon {@code join}. |
| 1153 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
| 1154 |
> |
* method of the given {@code Runnable} as its action, and returns |
| 1155 |
> |
* a null result upon {@link #join}. |
| 1156 |
|
* |
| 1157 |
|
* @param runnable the runnable action |
| 1158 |
|
* @return the task |
| 1159 |
|
*/ |
| 1160 |
< |
public static ForkJoinTask<Void> adapt(Runnable runnable) { |
| 1160 |
> |
public static ForkJoinTask<?> adapt(Runnable runnable) { |
| 1161 |
|
return new AdaptedRunnable<Void>(runnable, null); |
| 1162 |
|
} |
| 1163 |
|
|
| 1164 |
|
/** |
| 1165 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
| 1166 |
< |
* method of the given Runnable as its action, and returns the |
| 1167 |
< |
* given result upon {@code join}. |
| 1165 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
| 1166 |
> |
* method of the given {@code Runnable} as its action, and returns |
| 1167 |
> |
* the given result upon {@link #join}. |
| 1168 |
|
* |
| 1169 |
|
* @param runnable the runnable action |
| 1170 |
|
* @param result the result upon completion |
| 1175 |
|
} |
| 1176 |
|
|
| 1177 |
|
/** |
| 1178 |
< |
* Returns a new ForkJoinTask that performs the {@code call} |
| 1179 |
< |
* method of the given Callable as its action, and returns its |
| 1180 |
< |
* result upon {@code join}, translating any checked |
| 1181 |
< |
* exceptions encountered into {@code RuntimeException}. |
| 1178 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
| 1179 |
> |
* method of the given {@code Callable} as its action, and returns |
| 1180 |
> |
* its result upon {@link #join}, translating any checked exceptions |
| 1181 |
> |
* encountered into {@code RuntimeException}. |
| 1182 |
|
* |
| 1183 |
|
* @param callable the callable action |
| 1184 |
|
* @return the task |
| 1185 |
|
*/ |
| 1186 |
< |
public static <T> ForkJoinTask<T> adapt(Callable<T> callable) { |
| 1186 |
> |
public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) { |
| 1187 |
|
return new AdaptedCallable<T>(callable); |
| 1188 |
|
} |
| 1189 |
|
|
