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/* |
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* @(#)Future.java |
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*/ |
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|
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package java.util.concurrent; |
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|
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/** |
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* A <tt>Future</tt> represents the result of an asynchronous computation. |
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* Methods are provided to check if the computation is complete, |
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* to wait for its completion, and to retrieve the result of the |
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* computation. The result can only be retrieved when the computation |
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* has completed. The <tt>get</tt> method will block until the computation |
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* has completed. Once the computation has completed, the result cannot |
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* be changed, nor can the computation be restarted or cancelled. |
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* |
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* <p> |
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* <b>Sample Usage</b> <p> |
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* <pre> |
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* class Image { ... }; |
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* class ImageRenderer { Image render(byte[] raw); } |
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* class App { |
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* Executor executor = ... |
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* ImageRenderer renderer = ... |
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* void display(final byte[] rawimage) throws InterruptedException { |
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* Future futureImage = |
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* new FutureTask(new Callable() { |
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* public Object call() { |
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* return renderer.render(rawImage); |
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* }}); |
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* executor.execute(futureImage); |
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* drawBorders(); // do other things while executing |
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* drawCaption(); |
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* try { |
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* drawImage((Image)(futureImage.get())); // use future |
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* } |
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* catch (ExecutionException ex) { cleanup(); return; } |
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* } |
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* } |
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* </pre> |
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* |
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* @since 1.5 |
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* @see FutureTask |
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* @see Executor |
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* |
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* @spec JSR-166 |
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* @revised $Date: 2003/05/27 18:14:40 $ |
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* @editor $Author: dl $ |
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*/ |
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public interface Future<V> { |
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|
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/** |
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* Returns <tt>true</tt> if the underlying task has completed. |
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* |
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* @fixme relation to isDone in Cancellable? |
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* |
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* @return <tt>true</tt> if underlying task has completed |
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*/ |
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boolean isDone(); |
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|
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/** |
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* Waits if necessary for computation to complete, and then |
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* retrieves its result. |
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* |
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* @return computed result |
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* @throws CancellationException here??? |
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* @throws ExecutionException if underlying computation threw an exception |
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* @throws InterruptedException if current thread was interrupted while waiting |
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*/ |
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V get() throws InterruptedException, ExecutionException; |
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|
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/** |
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* Waits if necessary for at most the given time for the computation |
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* to complete, and then retrieves its result. |
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* |
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* @param timeout the maximum time to wait |
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* @param granularity the time unit of the timeout argument |
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* @return computed result |
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* @throws ExecutionException if underlying computation threw an exception |
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* @throws InterruptedException if current thread was interrupted while waiting |
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* @throws TimeoutException if the wait timed out |
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*/ |
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V get(long timeout, TimeUnit granularity) |
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throws InterruptedException, ExecutionException, TimeoutException; |
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} |
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