| 7 |
|
package java.util.concurrent; |
| 8 |
|
|
| 9 |
|
/** |
| 10 |
< |
* A semaphore that guarantees that threads invoking |
| 11 |
< |
* any of the {@link #acquire() acquire} methods |
| 12 |
< |
* are allocated permits in the order in |
| 13 |
< |
* which their invocation of those methods was processed (first-in-first-out). |
| 10 |
> |
* A semaphore guaranteeing that threads invoking any of the {@link |
| 11 |
> |
* #acquire() acquire} methods are allocated permits in the order in |
| 12 |
> |
* which their invocation of those methods was processed |
| 13 |
> |
* (first-in-first-out; FIFO). Note that FIFO ordering necessarily |
| 14 |
> |
* applies to specific internal points of execution within these |
| 15 |
> |
* methods. So, it is possible for one thread to invoke |
| 16 |
> |
* <tt>acquire</tt> before another, but reach the ordering point after |
| 17 |
> |
* the other, and similarly upon return from the method. |
| 18 |
|
* |
| 19 |
< |
* <p>This class introduces a fairness guarantee that can be useful |
| 20 |
< |
* in some contexts. |
| 21 |
< |
* However, it needs to be realized that the order in which invocations are |
| 18 |
< |
* processed can be different from the order in which an application perceives |
| 19 |
< |
* those invocations to be processed. Effectively, when no permit is available |
| 20 |
< |
* each thread is stored in a FIFO queue. As permits are released, they |
| 21 |
< |
* are allocated to the thread at the head of the queue, and so the order |
| 22 |
< |
* in which threads enter the queue, is the order in which they come out. |
| 23 |
< |
* This order need not have any relationship to the order in which requests |
| 24 |
< |
* were made, nor the order in which requests actually return to the caller as |
| 25 |
< |
* these depend on the underlying thread scheduling, which is not guaranteed |
| 26 |
< |
* to be predictable or fair. |
| 27 |
< |
* |
| 28 |
< |
* <p>As permits are allocated in-order, this class also provides convenience |
| 29 |
< |
* methods to {@link #acquire(long) acquire} and |
| 30 |
< |
* {@link #release(long) release} multiple permits at a time. |
| 19 |
> |
* <p>Because permits are allocated in-order, this class also provides |
| 20 |
> |
* convenience methods to {@link #acquire(long) acquire} and {@link |
| 21 |
> |
* #release(long) release} multiple permits at a time. |
| 22 |
|
* |
| 23 |
|
* @since 1.5 |
| 24 |
|
* @spec JSR-166 |
| 289 |
|
lock.unlock(); |
| 290 |
|
} |
| 291 |
|
} |
| 301 |
– |
|
| 302 |
– |
|
| 303 |
– |
|
| 292 |
|
} |
| 305 |
– |
|
| 306 |
– |
|
| 307 |
– |
|
| 308 |
– |
|
| 309 |
– |
|
