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*/ |
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package java.util.concurrent; |
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import java.util.concurrent.*; // for javadoc (till 6280605 is fixed) |
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/** |
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* A {@link CompletionService} that uses a supplied {@link Executor} |
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* could write this as: |
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* |
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* <pre> |
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* void solve(Executor e, Collection<Callable<Result>> solvers) |
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* throws InterruptedException, ExecutionException { |
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* CompletionService<Result> ecs = new ExecutorCompletionService<Result>(e); |
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* for (Callable<Result> s : solvers) |
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* ecs.submit(s); |
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* int n = solvers.size(); |
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* for (int i = 0; i < n; ++i) { |
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* Result r = ecs.take().get(); |
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* if (r != null) |
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* use(r); |
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* } |
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* } |
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* void solve(Executor e, |
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* Collection<Callable<Result>> solvers) |
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* throws InterruptedException, ExecutionException { |
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* CompletionService<Result> ecs |
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* = new ExecutorCompletionService<Result>(e); |
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* for (Callable<Result> s : solvers) |
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* ecs.submit(s); |
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* int n = solvers.size(); |
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* for (int i = 0; i < n; ++i) { |
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* Result r = ecs.take().get(); |
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* if (r != null) |
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* use(r); |
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* } |
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* } |
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* </pre> |
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* |
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* Suppose instead that you would like to use the first non-null result |
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* and cancelling all other tasks when the first one is ready: |
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* |
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* <pre> |
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* void solve(Executor e, Collection<Callable<Result>> solvers) |
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* throws InterruptedException { |
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* CompletionService<Result> ecs = new ExecutorCompletionService<Result>(e); |
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* int n = solvers.size(); |
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* List<Future<Result>> futures = new ArrayList<Future<Result>>(n); |
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* Result result = null; |
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* try { |
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* for (Callable<Result> s : solvers) |
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* futures.add(ecs.submit(s)); |
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* for (int i = 0; i < n; ++i) { |
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* try { |
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* Result r = ecs.take().get(); |
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* if (r != null) { |
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* result = r; |
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* break; |
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* } |
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* } catch (ExecutionException ignore) {} |
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* } |
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* } |
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* finally { |
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* for (Future<Result> f : futures) |
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* f.cancel(true); |
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* } |
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* |
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* if (result != null) |
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* use(result); |
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* } |
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* void solve(Executor e, |
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* Collection<Callable<Result>> solvers) |
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* throws InterruptedException { |
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* CompletionService<Result> ecs |
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* = new ExecutorCompletionService<Result>(e); |
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* int n = solvers.size(); |
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* List<Future<Result>> futures |
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* = new ArrayList<Future<Result>>(n); |
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* Result result = null; |
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* try { |
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* for (Callable<Result> s : solvers) |
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* futures.add(ecs.submit(s)); |
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* for (int i = 0; i < n; ++i) { |
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* try { |
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* Result r = ecs.take().get(); |
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* if (r != null) { |
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* result = r; |
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* break; |
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* } |
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* } catch (ExecutionException ignore) {} |
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* } |
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* } |
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* finally { |
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* for (Future<Result> f : futures) |
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* f.cancel(true); |
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* } |
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* |
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* if (result != null) |
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* use(result); |
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* } |
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* </pre> |
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*/ |
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public class ExecutorCompletionService<V> implements CompletionService<V> { |
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* Creates an ExecutorCompletionService using the supplied |
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* executor for base task execution and a |
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* {@link LinkedBlockingQueue} as a completion queue. |
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* |
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* @param executor the executor to use |
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* @throws NullPointerException if executor is <tt>null</tt> |
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*/ |
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* Creates an ExecutorCompletionService using the supplied |
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* executor for base task execution and the supplied queue as its |
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* completion queue. |
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+ |
* |
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* @param executor the executor to use |
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* @param completionQueue the queue to use as the completion queue |
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* normally one dedicated for use by this service |
