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. |
492 |
|
* #inForkJoinPool}). Attempts to invoke in other contexts result |
493 |
|
* in exceptions or errors, possibly including ClassCastException. |
494 |
|
* |
495 |
< |
* @return <code>this</code>, to simplify usage. |
495 |
> |
* @return {@code this}, to simplify usage. |
496 |
|
*/ |
497 |
|
public final ForkJoinTask<V> fork() { |
498 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
605 |
|
* in exceptions or errors, possibly including ClassCastException. |
606 |
|
* |
607 |
|
* @param tasks the collection of tasks |
608 |
+ |
* @return the tasks argument, to simplify usage |
609 |
|
* @throws NullPointerException if tasks or any element are null |
610 |
|
* @throws RuntimeException or Error if any task did so |
611 |
|
*/ |
612 |
< |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
612 |
> |
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
613 |
|
if (!(tasks instanceof List<?>)) { |
614 |
|
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
615 |
< |
return; |
615 |
> |
return tasks; |
616 |
|
} |
617 |
|
@SuppressWarnings("unchecked") |
618 |
|
List<? extends ForkJoinTask<?>> ts = |
647 |
|
} |
648 |
|
if (ex != null) |
649 |
|
rethrowException(ex); |
650 |
+ |
return tasks; |
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()) |
1041 |
|
// adaptors |
1042 |
|
|
1043 |
|
/** |
1044 |
< |
* Returns a new ForkJoinTask that performs the <code>run</code> |
1044 |
> |
* Returns a new ForkJoinTask that performs the {@code run} |
1045 |
|
* method of the given Runnable as its action, and returns a null |
1046 |
< |
* result upon <code>join</code>. |
1046 |
> |
* result upon {@code join}. |
1047 |
|
* |
1048 |
|
* @param runnable the runnable action |
1049 |
|
* @return the task |
1053 |
|
} |
1054 |
|
|
1055 |
|
/** |
1056 |
< |
* Returns a new ForkJoinTask that performs the <code>run</code> |
1056 |
> |
* Returns a new ForkJoinTask that performs the {@code run} |
1057 |
|
* method of the given Runnable as its action, and returns the |
1058 |
< |
* given result upon <code>join</code>. |
1058 |
> |
* given result upon {@code join}. |
1059 |
|
* |
1060 |
|
* @param runnable the runnable action |
1061 |
|
* @param result the result upon completion |
1066 |
|
} |
1067 |
|
|
1068 |
|
/** |
1069 |
< |
* Returns a new ForkJoinTask that performs the <code>call</code> |
1069 |
> |
* Returns a new ForkJoinTask that performs the {@code call} |
1070 |
|
* method of the given Callable as its action, and returns its |
1071 |
< |
* result upon <code>join</code>, translating any checked |
1072 |
< |
* exceptions encountered into <code>RuntimeException<code>. |
1071 |
> |
* result upon {@code join}, translating any checked |
1072 |
> |
* exceptions encountered into {@code RuntimeException}. |
1073 |
|
* |
1074 |
|
* @param callable the callable action |
1075 |
|
* @return the task |
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) |
1110 |
|
setDoneExceptionally((Throwable) ex); |
1111 |
|
} |
1112 |
|
|
1113 |
< |
// Unsafe mechanics for jsr166y 3rd party package. |
1113 |
> |
// Unsafe mechanics |
1114 |
> |
|
1115 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1116 |
> |
private static final long statusOffset = |
1117 |
> |
objectFieldOffset("status", ForkJoinTask.class); |
1118 |
> |
|
1119 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1120 |
> |
try { |
1121 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1122 |
> |
} catch (NoSuchFieldException e) { |
1123 |
> |
// Convert Exception to corresponding Error |
1124 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1125 |
> |
error.initCause(e); |
1126 |
> |
throw error; |
1127 |
> |
} |
1128 |
> |
} |
1129 |
> |
|
1130 |
> |
/** |
1131 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1132 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1133 |
> |
* into a jdk. |
1134 |
> |
* |
1135 |
> |
* @return a sun.misc.Unsafe |
1136 |
> |
*/ |
1137 |
|
private static sun.misc.Unsafe getUnsafe() { |
1138 |
|
try { |
1139 |
|
return sun.misc.Unsafe.getUnsafe(); |
1140 |
|
} catch (SecurityException se) { |
1141 |
|
try { |
1142 |
|
return java.security.AccessController.doPrivileged |
1143 |
< |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1143 |
> |
(new java.security |
1144 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1145 |
|
public sun.misc.Unsafe run() throws Exception { |
1146 |
< |
return getUnsafeByReflection(); |
1146 |
> |
java.lang.reflect.Field f = sun.misc |
1147 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1148 |
> |
f.setAccessible(true); |
1149 |
> |
return (sun.misc.Unsafe) f.get(null); |
1150 |
|
}}); |
1151 |
|
} catch (java.security.PrivilegedActionException e) { |
1152 |
|
throw new RuntimeException("Could not initialize intrinsics", |
1154 |
|
} |
1155 |
|
} |
1156 |
|
} |
1129 |
– |
|
1130 |
– |
private static sun.misc.Unsafe getUnsafeByReflection() |
1131 |
– |
throws NoSuchFieldException, IllegalAccessException { |
1132 |
– |
java.lang.reflect.Field f = |
1133 |
– |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
1134 |
– |
f.setAccessible(true); |
1135 |
– |
return (sun.misc.Unsafe) f.get(null); |
1136 |
– |
} |
1137 |
– |
|
1138 |
– |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
1139 |
– |
try { |
1140 |
– |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
1141 |
– |
} catch (NoSuchFieldException e) { |
1142 |
– |
// Convert Exception to Error |
1143 |
– |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
1144 |
– |
error.initCause(e); |
1145 |
– |
throw error; |
1146 |
– |
} |
1147 |
– |
} |
1148 |
– |
|
1149 |
– |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1150 |
– |
static final long statusOffset = |
1151 |
– |
fieldOffset("status", ForkJoinTask.class); |
1152 |
– |
|
1157 |
|
} |