src/share/classes/java/util/concurrent/Future.java

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*** 45,91 **** * <tt>cancel</tt> 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 <tt>Future</tt> for the sake * of cancellability but not provide a usable result, you can ! * declare types of the form <tt>Future&lt;?&gt;</tt> and * return <tt>null</tt> as a result of the underlying task. * * <p> * <b>Sample Usage</b> (Note that the following classes are all * made-up.) <p> ! * <pre> * interface ArchiveSearcher { String search(String target); } * class App { * ExecutorService executor = ... * ArchiveSearcher searcher = ... * void showSearch(final String target) * throws InterruptedException { ! * Future&lt;String&gt; future ! * = executor.submit(new Callable&lt;String&gt;() { * public String call() { * return searcher.search(target); * }}); * 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 <tt>Future</tt> that * implements <tt>Runnable</tt>, and so may be executed by an <tt>Executor</tt>. * For example, the above construction with <tt>submit</tt> could be replaced by: ! * <pre> ! * FutureTask&lt;String&gt; future = ! * new FutureTask&lt;String&gt;(new Callable&lt;String&gt;() { * public String call() { * return searcher.search(target); * }}); ! * 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. * --- 45,89 ---- * <tt>cancel</tt> 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 <tt>Future</tt> for the sake * of cancellability but not provide a usable result, you can ! * declare types of the form {@code Future<?>} and * return <tt>null</tt> as a result of the underlying task. * * <p> * <b>Sample Usage</b> (Note that the following classes are all * made-up.) <p> ! * <pre> {@code * interface ArchiveSearcher { String search(String target); } * class App { * ExecutorService executor = ... * ArchiveSearcher searcher = ... * void showSearch(final String target) * throws InterruptedException { ! * Future<String> future ! * = executor.submit(new Callable<String>() { * public String call() { * return searcher.search(target); * }}); * 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 <tt>Future</tt> that * implements <tt>Runnable</tt>, and so may be executed by an <tt>Executor</tt>. * For example, the above construction with <tt>submit</tt> could be replaced by: ! * <pre> {@code ! * FutureTask<String> future = ! * new FutureTask<String>(new Callable<String>() { * public String call() { * return searcher.search(target); * }}); ! * 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. *