MoreFutures { public static <T> void mirror(ListenableFuture<? extends T> source, SettableFuture<? super T> destination, boolean mayInterruptIfRunning) { FutureCallback<T> callback = new FutureCallback<T>() { @Override public void onSuccess(@Nullable T result) { destination.set(result); } @Override public void onFailure(Throwable t) { destination.setException(t); } }; Futures.addCallback(source, callback, directExecutor()); propagateCancellation(destination, source, mayInterruptIfRunning); } private  MoreFutures(); static void propagateCancellation(ListenableFuture<? extends X> source, Future<? extends Y> destination, boolean mayInterruptIfRunning); static void mirror(ListenableFuture<? extends T> source, SettableFuture<? super T> destination, boolean mayInterruptIfRunning); static Throwable unwrapCompletionException(Throwable throwable); static CompletableFuture<V> unmodifiableFuture(CompletableFuture<V> future); static CompletableFuture<V> unmodifiableFuture(CompletableFuture<V> future, boolean propagateCancel); static CompletableFuture<V> failedFuture(Throwable throwable); static V getFutureValue(Future<V> future); static V getFutureValue(Future<V> future, Class<E> exceptionType); static Optional<T> tryGetFutureValue(Future<T> future); static Optional<V> tryGetFutureValue(Future<V> future, int timeout, TimeUnit timeUnit); static Optional<V> tryGetFutureValue(Future<V> future, int timeout, TimeUnit timeUnit, Class<E> exceptionType); static T getDone(Future<T> future); static void checkSuccess(Future<?> future, String errorMessage); static ListenableFuture<V> whenAnyComplete(Iterable<? extends ListenableFuture<? extends V>> futures); static ListenableFuture<V> whenAnyCompleteCancelOthers(Iterable<? extends ListenableFuture<? extends V>> futures); static CompletableFuture<V> firstCompletedFuture(Iterable<? extends CompletionStage<? extends V>> futures); static CompletableFuture<V> firstCompletedFuture(Iterable<? extends CompletionStage<? extends V>> futures, boolean propagateCancel); static CompletableFuture<List<V>> allAsList(List<CompletableFuture<? extends V>> futures); static ListenableFuture<T> addTimeout(ListenableFuture<T> future, Callable<T> onTimeout, Duration timeout, ScheduledExecutorService executorService); static CompletableFuture<T> addTimeout(CompletableFuture<T> future, Callable<T> onTimeout, Duration timeout, ScheduledExecutorService executorService); static CompletableFuture<V> toCompletableFuture(ListenableFuture<V> listenableFuture); static ListenableFuture<V> toListenableFuture(CompletableFuture<V> completableFuture); static void addSuccessCallback(ListenableFuture<T> future, Consumer<T> successCallback); static void addSuccessCallback(ListenableFuture<T> future, Runnable successCallback); static void addExceptionCallback(ListenableFuture<T> future, Consumer<Throwable> exceptionCallback); static void addExceptionCallback(ListenableFuture<T> future, Runnable exceptionCallback);  }
@Test public void testMirror() throws Exception { ExtendedSettableFuture<String> fromFuture = ExtendedSettableFuture.create(); SettableFuture<String> toFuture = SettableFuture.create(); mirror(fromFuture, toFuture, true); fromFuture.set("abc"); assertEquals(toFuture.get(), "abc"); fromFuture = ExtendedSettableFuture.create(); toFuture = SettableFuture.create(); mirror(fromFuture, toFuture, true); fromFuture.setException(new RuntimeException()); assertThrows(ExecutionException.class, toFuture::get); fromFuture = ExtendedSettableFuture.create(); toFuture = SettableFuture.create(); mirror(fromFuture, toFuture, false); toFuture.cancel(true); assertTrue(fromFuture.isCancelled()); assertFalse(fromFuture.checkWasInterrupted()); fromFuture = ExtendedSettableFuture.create(); toFuture = SettableFuture.create(); mirror(fromFuture, toFuture, true); toFuture.cancel(false); assertTrue(fromFuture.isCancelled()); assertTrue(fromFuture.checkWasInterrupted()); }