| 12 |
|
* complete, to wait for its completion, and to retrieve the result of |
| 13 |
|
* the computation. The result can only be retrieved using method |
| 14 |
|
* <tt>get</tt> when the computation has completed, blocking if |
| 15 |
< |
* necessary until it is ready. Once the computation has completed, |
| 16 |
< |
* the computation cannot be cancelled. |
| 15 |
> |
* necessary until it is ready. Cancellation is performed by the |
| 16 |
> |
* <tt>cancel</tt> method. Additional methods are provided to |
| 17 |
> |
* determine if the task completed normally or was cancelled. Once a |
| 18 |
> |
* computation has completed, the computation cannot be cancelled. |
| 19 |
|
* |
| 20 |
|
* <p> |
| 21 |
|
* <b>Sample Usage</b> (Note that the following classes are all |
| 56 |
|
* @author Doug Lea |
| 57 |
|
* @param <V> The result type returned by this Future's <tt>get</tt> method |
| 58 |
|
*/ |
| 59 |
< |
public interface Future<V> extends Cancellable { |
| 59 |
> |
public interface Future<V> { |
| 60 |
> |
|
| 61 |
> |
/** |
| 62 |
> |
* Attempts to cancel execution of this task. This attempt will |
| 63 |
> |
* fail if the task has already completed, already been cancelled, |
| 64 |
> |
* or could not be cancelled for some other reason. If successful, |
| 65 |
> |
* and this task has not started when <tt>cancel</tt> is called, |
| 66 |
> |
* this task should never run. If the task has already started, |
| 67 |
> |
* then the <tt>interruptIfRunning</tt> parameter determines |
| 68 |
> |
* whether the thread executing this task should be interrupted in |
| 69 |
> |
* an attempt to stop the task. |
| 70 |
> |
* |
| 71 |
> |
* @param mayInterruptIfRunning <tt>true</tt> if the thread executing this |
| 72 |
> |
* task should be interrupted; otherwise, in-progress tasks are allowed |
| 73 |
> |
* to complete |
| 74 |
> |
* @return <tt>false</tt> if the task could not be cancelled, |
| 75 |
> |
* typically because is has already completed normally; |
| 76 |
> |
* <tt>true</tt> otherwise |
| 77 |
> |
*/ |
| 78 |
> |
boolean cancel(boolean mayInterruptIfRunning); |
| 79 |
> |
|
| 80 |
> |
/** |
| 81 |
> |
* Returns <tt>true</tt> if this task was cancelled before it completed |
| 82 |
> |
* normally. |
| 83 |
> |
* |
| 84 |
> |
* @return <tt>true</tt> if task was cancelled before it completed |
| 85 |
> |
*/ |
| 86 |
> |
boolean isCancelled(); |
| 87 |
> |
|
| 88 |
> |
/** |
| 89 |
> |
* Returns <tt>true</tt> if this task completed. |
| 90 |
> |
* |
| 91 |
> |
* Completion may be due to normal termination, an exception, or |
| 92 |
> |
* cancellation -- in all of these cases, this method will return |
| 93 |
> |
* <tt>true</tt>. |
| 94 |
> |
* |
| 95 |
> |
* @return <tt>true</tt> if this task completed. |
| 96 |
> |
*/ |
| 97 |
> |
boolean isDone(); |
| 98 |
|
|
| 99 |
|
/** |
| 100 |
|
* Waits if necessary for computation to complete, and then |
