| 20 |
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* a {@link CyclicBarrier}. |
| 21 |
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* |
| 22 |
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* <p>A <tt>CountDownLatch</tt> is a versatile synchronization tool |
| 23 |
< |
* and can be used for a number of purposes. |
| 24 |
< |
* A <tt>CountDownLatch</tt> initialized with a count of one serves as a simple on/off |
| 25 |
< |
* latch, or gate: all threads invoking {@link #await} wait at the gate until |
| 26 |
< |
* it is opened by a thread invoking {@link #countDown}. |
| 27 |
< |
* A <tt>CountDownLatch</tt> initialized to <em>N</em> can be used to make |
| 28 |
< |
* one thread wait until <em>N</em> threads have completed some action, or some |
| 29 |
< |
* action has been completed N times. |
| 30 |
< |
* <p>A useful property of a <tt>CountDownLatch</tt> is that it doesn't |
| 31 |
< |
* require that threads calling <tt>countDown</tt> wait for the count to reach zero |
| 32 |
< |
* before proceeding, it simply |
| 33 |
< |
* prevents any thread from proceeding past the {@link #await wait} until |
| 34 |
< |
* all threads could pass. |
| 23 |
> |
* and can be used for a number of purposes. A |
| 24 |
> |
* <tt>CountDownLatch</tt> initialized with a count of one serves as a |
| 25 |
> |
* simple on/off latch, or gate: all threads invoking {@link #await} |
| 26 |
> |
* wait at the gate until it is opened by a thread invoking {@link |
| 27 |
> |
* #countDown}. A <tt>CountDownLatch</tt> initialized to <em>N</em> |
| 28 |
> |
* can be used to make one thread wait until <em>N</em> threads have |
| 29 |
> |
* completed some action, or some action has been completed N times. |
| 30 |
> |
* <p>A useful property of a <tt>CountDownLatch</tt> is that it |
| 31 |
> |
* doesn't require that threads calling <tt>countDown</tt> wait for |
| 32 |
> |
* the count to reach zero before proceeding, it simply prevents any |
| 33 |
> |
* thread from proceeding past the {@link #await wait} until all |
| 34 |
> |
* threads could pass. |
| 35 |
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* |
| 36 |
|
* <p><b>Sample usage:</b> Here is a pair of classes in which a group |
| 37 |
|
* of worker threads use two countdown latches: |
| 79 |
|
* |
| 80 |
|
* </pre> |
| 81 |
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* |
| 82 |
< |
* <p>Another typical usage would be to divide a problem into N parts, describe each part |
| 83 |
< |
* with a Runnable that executes that portion and counts down on the latch, and queue all |
| 84 |
< |
* the Runnables to an Executor. When all sub-parts are complete, the coordinating thread |
| 82 |
> |
* <p>Another typical usage would be to divide a problem into N parts, |
| 83 |
> |
* describe each part with a Runnable that executes that portion and |
| 84 |
> |
* counts down on the latch, and queue all the Runnables to an |
| 85 |
> |
* Executor. When all sub-parts are complete, the coordinating thread |
| 86 |
|
* will be able to pass through await. |
| 87 |
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* |
| 88 |
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* <pre> |
| 122 |
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* @spec JSR-166 |
| 123 |
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* @revised $Date$ |
| 124 |
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* @editor $Author$ |
| 125 |
+ |
* @author Doug Lea |
| 126 |
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*/ |
| 127 |
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public class CountDownLatch { |
| 128 |
|
private final ReentrantLock lock = new ReentrantLock(); |
