Waits if necessary for the computation to complete, and then retrieves its result.
Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.
Attempts to cancel execution of this task. This attempt will fail if the task has already completed, has already been cancelled, or could not be cancelled for some other reason. If successful, and this task has not started when {@code cancel} is called, this task should never run. If the task has already started, then the {@code mayInterruptIfRunning} parameter determines whether the thread executing this task should be interrupted in an attempt to stop the task.
Returns {@code true} if this task was cancelled before it completed normally.
Returns {@code true} if this task completed.
A {@code Future} represents the result of an asynchronous computation. Methods are provided to check if the computation is complete, to wait for its completion, and to retrieve the result of the computation. The result can only be retrieved using method {@code get} when the computation has completed, blocking if necessary until it is ready. Cancellation is performed by the {@code cancel} method. Additional methods are provided to determine if the task completed normally or was cancelled. Once a computation has completed, the computation cannot be cancelled. If you would like to use a {@code Future} for the sake of cancellability but not provide a usable result, you can declare types of the form {@code Future<?>} and return {@code null} as a result of the underlying task.
<p><b>Sample Usage</b> (Note that the following classes are all made-up.)
<pre> {@code interface ArchiveSearcher { string search(string target); } class App { ExecutorService executor = ... ArchiveSearcher searcher = ... void showSearch(string target) throws InterruptedException { Callable!(string) task = () -> searcher.search(target); Future!(string) future = executor.submit(task); displayOtherThings(); // do other things while searching try { displayText(future.get()); // use future } catch (ExecutionException ex) { cleanup(); return; } } }}</pre>
The {@link FutureTask} class is an implementation of {@code Future} that implements {@code Runnable}, and so may be executed by an {@code Executor}. For example, the above construction with {@code submit} could be replaced by: <pre> {@code FutureTask!(string) future = new FutureTask<>(task); executor.execute(future);}</pre>
<p>Memory consistency effects: Actions taken by the asynchronous computation <a href="package-summary.html#MemoryVisibility"> <i>happen-before</i></a> actions following the corresponding {@code Future.get()} in another thread.
@see FutureTask @see Executor @author Doug Lea @param (V) The result type returned by this Future's {@code get} method