| 192 |
|
* simple feedback control mechanism that will slow down the rate that |
| 193 |
|
* new tasks are submitted. |
| 194 |
|
* |
| 195 |
< |
* <li>In {@link ThreadPoolExecutor.DiscardPolicy}, a task that |
| 196 |
< |
* cannot be executed is simply dropped. |
| 195 |
> |
* <li>In {@link ThreadPoolExecutor.DiscardPolicy}, a task that cannot |
| 196 |
> |
* be executed is simply dropped. This policy is designed only for |
| 197 |
> |
* those rare cases in which task completion is never relied upon. |
| 198 |
|
* |
| 199 |
|
* <li>In {@link ThreadPoolExecutor.DiscardOldestPolicy}, if the |
| 200 |
|
* executor is not shut down, the task at the head of the work queue |
| 201 |
|
* is dropped, and then execution is retried (which can fail again, |
| 202 |
< |
* causing this to be repeated.) |
| 202 |
> |
* causing this to be repeated.) This policy is rarely acceptable. In |
| 203 |
> |
* nearly all cases, you should also cancel the task to cause an |
| 204 |
> |
* exception in any component waiting for its completion, and/or log |
| 205 |
> |
* the failure, as illustrated in {@link |
| 206 |
> |
* ThreadPoolExecutor.DiscardOldestPolicy} documentation. |
| 207 |
|
* |
| 208 |
|
* </ol> |
| 209 |
|
* |
| 2057 |
|
/** |
| 2058 |
|
* A handler for rejected tasks that discards the oldest unhandled |
| 2059 |
|
* request and then retries {@code execute}, unless the executor |
| 2060 |
< |
* is shut down, in which case the task is discarded. |
| 2060 |
> |
* is shut down, in which case the task is discarded. This policy is |
| 2061 |
> |
* rarely useful in cases where other threads may be waiting for |
| 2062 |
> |
* tasks to terminate, or failures must be recorded. Instead consider |
| 2063 |
> |
* using a handler of the form: |
| 2064 |
> |
* <pre> {@code |
| 2065 |
> |
* new RejectedExecutionHandler() { |
| 2066 |
> |
* public void rejectedExecution(Runnable r, ThreadPoolExecutor e) { |
| 2067 |
> |
* Future<?> dropped = e.getQueue().poll(); |
| 2068 |
> |
* if (dropped != null) |
| 2069 |
> |
* dropped.cancel(false); // also consider logging the failure |
| 2070 |
> |
* e.execute(r); // retry |
| 2071 |
> |
* }}}</pre> |
| 2072 |
|
*/ |
| 2073 |
|
public static class DiscardOldestPolicy implements RejectedExecutionHandler { |
| 2074 |
|
/** |
