--- jsr166/src/test/tck/CompletableFutureTest.java 2015/09/04 02:50:00 1.109 +++ jsr166/src/test/tck/CompletableFutureTest.java 2015/10/02 21:08:48 1.126 @@ -8,9 +8,17 @@ import static java.util.concurrent.TimeUnit.MILLISECONDS; import static java.util.concurrent.TimeUnit.SECONDS; +import java.lang.reflect.Method; +import java.lang.reflect.Modifier; + +import java.util.stream.Collectors; +import java.util.stream.Stream; + import java.util.ArrayList; +import java.util.Arrays; import java.util.List; import java.util.Objects; +import java.util.Set; import java.util.concurrent.Callable; import java.util.concurrent.CancellationException; import java.util.concurrent.CompletableFuture; @@ -28,6 +36,7 @@ import java.util.function.BiConsumer; import java.util.function.BiFunction; import java.util.function.Consumer; import java.util.function.Function; +import java.util.function.Predicate; import java.util.function.Supplier; import junit.framework.Test; @@ -77,142 +86,94 @@ public class CompletableFutureTest exten assertTrue(f.toString().contains("[Completed normally]")); } - void checkCompletedWithWrappedCFException(CompletableFuture f) { - long startTime = System.nanoTime(); - long timeoutMillis = LONG_DELAY_MS; - try { - f.get(timeoutMillis, MILLISECONDS); - shouldThrow(); - } catch (ExecutionException success) { - assertTrue(success.getCause() instanceof CFException); - } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) < timeoutMillis/2); - - try { - f.join(); - shouldThrow(); - } catch (CompletionException success) { - assertTrue(success.getCause() instanceof CFException); - } - try { - f.getNow(null); - shouldThrow(); - } catch (CompletionException success) { - assertTrue(success.getCause() instanceof CFException); + /** + * Returns the "raw" internal exceptional completion of f, + * without any additional wrapping with CompletionException. + */ + Throwable exceptionalCompletion(CompletableFuture f) { + // handle (and whenComplete) can distinguish between "direct" + // and "wrapped" exceptional completion + return f.handle((U u, Throwable t) -> t).join(); + } + + void checkCompletedExceptionally(CompletableFuture f, + boolean wrapped, + Consumer checker) { + Throwable cause = exceptionalCompletion(f); + if (wrapped) { + assertTrue(cause instanceof CompletionException); + cause = cause.getCause(); } - try { - f.get(); - shouldThrow(); - } catch (ExecutionException success) { - assertTrue(success.getCause() instanceof CFException); - } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(f.isDone()); - assertFalse(f.isCancelled()); - assertTrue(f.toString().contains("[Completed exceptionally]")); - } + checker.accept(cause); - void checkCompletedExceptionallyWithRootCause(CompletableFuture f, - Throwable ex) { long startTime = System.nanoTime(); - long timeoutMillis = LONG_DELAY_MS; try { - f.get(timeoutMillis, MILLISECONDS); + f.get(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (ExecutionException success) { - assertSame(ex, success.getCause()); + assertSame(cause, success.getCause()); } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) < timeoutMillis/2); + assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2); try { f.join(); shouldThrow(); } catch (CompletionException success) { - assertSame(ex, success.getCause()); - } + assertSame(cause, success.getCause()); + } catch (Throwable fail) { threadUnexpectedException(fail); } + try { f.getNow(null); shouldThrow(); } catch (CompletionException success) { - assertSame(ex, success.getCause()); - } + assertSame(cause, success.getCause()); + } catch (Throwable fail) { threadUnexpectedException(fail); } + try { f.get(); shouldThrow(); } catch (ExecutionException success) { - assertSame(ex, success.getCause()); + assertSame(cause, success.getCause()); } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(f.isDone()); assertFalse(f.isCancelled()); + assertTrue(f.isDone()); + assertTrue(f.isCompletedExceptionally()); assertTrue(f.toString().contains("[Completed exceptionally]")); } - void checkCompletedExceptionallyWithTimeout(CompletableFuture f) { - long startTime = System.nanoTime(); - long timeoutMillis = LONG_DELAY_MS; - try { - f.get(timeoutMillis, MILLISECONDS); - shouldThrow(); - } catch (ExecutionException ex) { - assertTrue(ex.getCause() instanceof TimeoutException); - } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) < timeoutMillis/2); - - try { - f.join(); - shouldThrow(); - } catch (Throwable ex) { - assertTrue(ex.getCause() instanceof TimeoutException); - } - - try { - f.getNow(null); - shouldThrow(); - } catch (Throwable ex) { - assertTrue(ex.getCause() instanceof TimeoutException); - } + void checkCompletedWithWrappedCFException(CompletableFuture f) { + checkCompletedExceptionally(f, true, + (t) -> assertTrue(t instanceof CFException)); + } - try { - f.get(); - shouldThrow(); - } catch (ExecutionException ex) { - assertTrue(ex.getCause() instanceof TimeoutException); - } catch (Throwable fail) { threadUnexpectedException(fail); } + void checkCompletedWithWrappedCancellationException(CompletableFuture f) { + checkCompletedExceptionally(f, true, + (t) -> assertTrue(t instanceof CancellationException)); + } - assertTrue(f.isDone()); - assertFalse(f.isCancelled()); - assertTrue(f.toString().contains("[Completed exceptionally]")); + void checkCompletedWithTimeoutException(CompletableFuture f) { + checkCompletedExceptionally(f, false, + (t) -> assertTrue(t instanceof TimeoutException)); } - void checkCompletedWithWrappedException(CompletableFuture f, - Throwable ex) { - checkCompletedExceptionallyWithRootCause(f, ex); - try { - CompletableFuture spy = f.handle - ((U u, Throwable t) -> t); - assertTrue(spy.join() instanceof CompletionException); - assertSame(ex, spy.join().getCause()); - } catch (Throwable fail) { threadUnexpectedException(fail); } + void checkCompletedWithWrappedException(CompletableFuture f, + Throwable ex) { + checkCompletedExceptionally(f, true, (t) -> assertSame(t, ex)); } - void checkCompletedExceptionally(CompletableFuture f, Throwable ex) { - checkCompletedExceptionallyWithRootCause(f, ex); - try { - CompletableFuture spy = f.handle - ((U u, Throwable t) -> t); - assertSame(ex, spy.join()); - } catch (Throwable fail) { threadUnexpectedException(fail); } + void checkCompletedExceptionally(CompletableFuture f, Throwable ex) { + checkCompletedExceptionally(f, false, (t) -> assertSame(t, ex)); } void checkCancelled(CompletableFuture f) { long startTime = System.nanoTime(); - long timeoutMillis = LONG_DELAY_MS; try { - f.get(timeoutMillis, MILLISECONDS); + f.get(LONG_DELAY_MS, MILLISECONDS); shouldThrow(); } catch (CancellationException success) { } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) < timeoutMillis/2); + assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2); try { f.join(); @@ -227,44 +188,12 @@ public class CompletableFutureTest exten shouldThrow(); } catch (CancellationException success) { } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(f.isDone()); - assertTrue(f.isCompletedExceptionally()); - assertTrue(f.isCancelled()); - assertTrue(f.toString().contains("[Completed exceptionally]")); - } - void checkCompletedWithWrappedCancellationException(CompletableFuture f) { - long startTime = System.nanoTime(); - long timeoutMillis = LONG_DELAY_MS; - try { - f.get(timeoutMillis, MILLISECONDS); - shouldThrow(); - } catch (ExecutionException success) { - assertTrue(success.getCause() instanceof CancellationException); - } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) < timeoutMillis/2); + assertTrue(exceptionalCompletion(f) instanceof CancellationException); - try { - f.join(); - shouldThrow(); - } catch (CompletionException success) { - assertTrue(success.getCause() instanceof CancellationException); - } - try { - f.getNow(null); - shouldThrow(); - } catch (CompletionException success) { - assertTrue(success.getCause() instanceof CancellationException); - } - try { - f.get(); - shouldThrow(); - } catch (ExecutionException success) { - assertTrue(success.getCause() instanceof CancellationException); - } catch (Throwable fail) { threadUnexpectedException(fail); } assertTrue(f.isDone()); - assertFalse(f.isCancelled()); assertTrue(f.isCompletedExceptionally()); + assertTrue(f.isCancelled()); assertTrue(f.toString().contains("[Completed exceptionally]")); } @@ -969,7 +898,7 @@ public class CompletableFutureTest exten * whenComplete action executes on normal completion, propagating * source result. */ - public void testWhenComplete_normalCompletion1() { + public void testWhenComplete_normalCompletion() { for (ExecutionMode m : ExecutionMode.values()) for (boolean createIncomplete : new boolean[] { true, false }) for (Integer v1 : new Integer[] { 1, null }) @@ -3142,7 +3071,7 @@ public class CompletableFutureTest exten for (int i = 0; i < k; i++) { checkIncomplete(f); checkIncomplete(CompletableFuture.allOf(fs)); - if (i != k/2) { + if (i != k / 2) { fs[i].complete(i); checkCompletedNormally(fs[i], i); } else { @@ -3345,6 +3274,16 @@ public class CompletableFutureTest exten () -> CompletableFuture.anyOf(null, f), () -> f.obtrudeException(null), + + () -> CompletableFuture.delayedExecutor(1L, SECONDS, null), + () -> CompletableFuture.delayedExecutor(1L, null, new ThreadExecutor()), + () -> CompletableFuture.delayedExecutor(1L, null), + + () -> f.orTimeout(1L, null), + () -> f.completeOnTimeout(42, 1L, null), + + () -> CompletableFuture.failedFuture(null), + () -> CompletableFuture.failedStage(null), }; assertThrows(NullPointerException.class, throwingActions); @@ -3365,17 +3304,25 @@ public class CompletableFutureTest exten * newIncompleteFuture returns an incomplete CompletableFuture */ public void testNewIncompleteFuture() { + for (Integer v1 : new Integer[] { 1, null }) + { CompletableFuture f = new CompletableFuture<>(); CompletableFuture g = f.newIncompleteFuture(); checkIncomplete(f); checkIncomplete(g); - } + f.complete(v1); + checkCompletedNormally(f, v1); + checkIncomplete(g); + g.complete(v1); + checkCompletedNormally(g, v1); + assertSame(g.getClass(), CompletableFuture.class); + }} /** * completedStage returns a completed CompletionStage */ public void testCompletedStage() { - AtomicInteger x = new AtomicInteger(); + AtomicInteger x = new AtomicInteger(0); AtomicReference r = new AtomicReference(); CompletionStage f = CompletableFuture.completedStage(1); f.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);}); @@ -3385,7 +3332,7 @@ public class CompletableFutureTest exten /** * defaultExecutor by default returns the commonPool if - * it supports at least one thread. + * it supports more than one thread. */ public void testDefaultExecutor() { CompletableFuture f = new CompletableFuture<>(); @@ -3393,6 +3340,8 @@ public class CompletableFutureTest exten Executor c = ForkJoinPool.commonPool(); if (ForkJoinPool.getCommonPoolParallelism() > 1) assertSame(e, c); + else + assertNotSame(e, c); } /** @@ -3402,13 +3351,13 @@ public class CompletableFutureTest exten public void testFailedFuture() { CFException ex = new CFException(); CompletableFuture f = CompletableFuture.failedFuture(ex); - checkCompletedExceptionallyWithRootCause(f, ex); + checkCompletedExceptionally(f, ex); } /** * failedFuture(null) throws NPE */ - public void testFailedFuture2() { + public void testFailedFuture_null() { try { CompletableFuture f = CompletableFuture.failedFuture(null); shouldThrow(); @@ -3441,7 +3390,7 @@ public class CompletableFutureTest exten CFException ex = new CFException(); f.completeExceptionally(ex); checkCompletedExceptionally(f, ex); - checkCompletedWithWrappedCFException(g); + checkCompletedWithWrappedException(g, ex); } /** @@ -3451,7 +3400,7 @@ public class CompletableFutureTest exten public void testMinimalCompletionStage() { CompletableFuture f = new CompletableFuture<>(); CompletionStage g = f.minimalCompletionStage(); - AtomicInteger x = new AtomicInteger(); + AtomicInteger x = new AtomicInteger(0); AtomicReference r = new AtomicReference(); checkIncomplete(f); g.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);}); @@ -3468,7 +3417,7 @@ public class CompletableFutureTest exten public void testMinimalCompletionStage2() { CompletableFuture f = new CompletableFuture<>(); CompletionStage g = f.minimalCompletionStage(); - AtomicInteger x = new AtomicInteger(); + AtomicInteger x = new AtomicInteger(0); AtomicReference r = new AtomicReference(); g.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);}); checkIncomplete(f); @@ -3486,22 +3435,24 @@ public class CompletableFutureTest exten public void testFailedStage() { CFException ex = new CFException(); CompletionStage f = CompletableFuture.failedStage(ex); - AtomicInteger x = new AtomicInteger(); + AtomicInteger x = new AtomicInteger(0); AtomicReference r = new AtomicReference(); f.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);}); assertEquals(x.get(), 0); - assertEquals(r.get().getCause(), ex); + assertEquals(r.get(), ex); } /** * completeAsync completes with value of given supplier */ public void testCompleteAsync() { + for (Integer v1 : new Integer[] { 1, null }) + { CompletableFuture f = new CompletableFuture<>(); - f.completeAsync(() -> 1); + f.completeAsync(() -> v1); f.join(); - checkCompletedNormally(f, 1); - } + checkCompletedNormally(f, v1); + }} /** * completeAsync completes exceptionally if given supplier throws @@ -3513,19 +3464,23 @@ public class CompletableFutureTest exten try { f.join(); shouldThrow(); - } catch (Exception success) {} - checkCompletedWithWrappedCFException(f); + } catch (CompletionException success) {} + checkCompletedWithWrappedException(f, ex); } /** * completeAsync with given executor completes with value of given supplier */ public void testCompleteAsync3() { + for (Integer v1 : new Integer[] { 1, null }) + { CompletableFuture f = new CompletableFuture<>(); - f.completeAsync(() -> 1, new ThreadExecutor()); - f.join(); - checkCompletedNormally(f, 1); - } + ThreadExecutor executor = new ThreadExecutor(); + f.completeAsync(() -> v1, executor); + assertSame(v1, f.join()); + checkCompletedNormally(f, v1); + assertEquals(1, executor.count.get()); + }} /** * completeAsync with given executor completes exceptionally if @@ -3534,87 +3489,122 @@ public class CompletableFutureTest exten public void testCompleteAsync4() { CompletableFuture f = new CompletableFuture<>(); CFException ex = new CFException(); - f.completeAsync(() -> {if (true) throw ex; return 1;}, new ThreadExecutor()); + ThreadExecutor executor = new ThreadExecutor(); + f.completeAsync(() -> {if (true) throw ex; return 1;}, executor); try { f.join(); shouldThrow(); - } catch (Exception success) {} - checkCompletedWithWrappedCFException(f); + } catch (CompletionException success) {} + checkCompletedWithWrappedException(f, ex); + assertEquals(1, executor.count.get()); } /** * orTimeout completes with TimeoutException if not complete */ - public void testOrTimeout() { + public void testOrTimeout_timesOut() { + long timeoutMillis = timeoutMillis(); CompletableFuture f = new CompletableFuture<>(); - f.orTimeout(SHORT_DELAY_MS, TimeUnit.MILLISECONDS); - checkCompletedExceptionallyWithTimeout(f); + long startTime = System.nanoTime(); + f.orTimeout(timeoutMillis, MILLISECONDS); + checkCompletedWithTimeoutException(f); + assertTrue(millisElapsedSince(startTime) >= timeoutMillis); } /** * orTimeout completes normally if completed before timeout */ - public void testOrTimeout2() { + public void testOrTimeout_completed() { + for (Integer v1 : new Integer[] { 1, null }) + { CompletableFuture f = new CompletableFuture<>(); - f.complete(1); - f.orTimeout(SHORT_DELAY_MS, TimeUnit.MILLISECONDS); - checkCompletedNormally(f, 1); - } + CompletableFuture g = new CompletableFuture<>(); + long startTime = System.nanoTime(); + f.complete(v1); + f.orTimeout(LONG_DELAY_MS, MILLISECONDS); + g.orTimeout(LONG_DELAY_MS, MILLISECONDS); + g.complete(v1); + checkCompletedNormally(f, v1); + checkCompletedNormally(g, v1); + assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2); + }} /** * completeOnTimeout completes with given value if not complete */ - public void testCompleteOnTimeout() { + public void testCompleteOnTimeout_timesOut() { + testInParallel(() -> testCompleteOnTimeout_timesOut(42), + () -> testCompleteOnTimeout_timesOut(null)); + } + + public void testCompleteOnTimeout_timesOut(Integer v) { + long timeoutMillis = timeoutMillis(); CompletableFuture f = new CompletableFuture<>(); - f.completeOnTimeout(-1, SHORT_DELAY_MS, TimeUnit.MILLISECONDS); - f.join(); - checkCompletedNormally(f, -1); + long startTime = System.nanoTime(); + f.completeOnTimeout(v, timeoutMillis, MILLISECONDS); + assertSame(v, f.join()); + assertTrue(millisElapsedSince(startTime) >= timeoutMillis); + f.complete(99); // should have no effect + checkCompletedNormally(f, v); } /** * completeOnTimeout has no effect if completed within timeout */ - public void testCompleteOnTimeout2() { + public void testCompleteOnTimeout_completed() { + for (Integer v1 : new Integer[] { 1, null }) + { CompletableFuture f = new CompletableFuture<>(); - f.complete(1); - f.completeOnTimeout(-1, SHORT_DELAY_MS, TimeUnit.MILLISECONDS); - checkCompletedNormally(f, 1); - } + CompletableFuture g = new CompletableFuture<>(); + long startTime = System.nanoTime(); + f.complete(v1); + f.completeOnTimeout(-1, LONG_DELAY_MS, MILLISECONDS); + g.completeOnTimeout(-1, LONG_DELAY_MS, MILLISECONDS); + g.complete(v1); + checkCompletedNormally(f, v1); + checkCompletedNormally(g, v1); + assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2); + }} /** * delayedExecutor returns an executor that delays submission */ public void testDelayedExecutor() { - long timeoutMillis = SMALL_DELAY_MS; - Executor d = CompletableFuture.delayedExecutor(timeoutMillis, - MILLISECONDS); + testInParallel(() -> testDelayedExecutor(null, null), + () -> testDelayedExecutor(null, 1), + () -> testDelayedExecutor(new ThreadExecutor(), 1), + () -> testDelayedExecutor(new ThreadExecutor(), 1)); + } + + public void testDelayedExecutor(Executor executor, Integer v) throws Exception { + long timeoutMillis = timeoutMillis(); + // Use an "unreasonably long" long timeout to catch lingering threads + long longTimeoutMillis = 1000 * 60 * 60 * 24; + final Executor delayer, longDelayer; + if (executor == null) { + delayer = CompletableFuture.delayedExecutor(timeoutMillis, MILLISECONDS); + longDelayer = CompletableFuture.delayedExecutor(longTimeoutMillis, MILLISECONDS); + } else { + delayer = CompletableFuture.delayedExecutor(timeoutMillis, MILLISECONDS, executor); + longDelayer = CompletableFuture.delayedExecutor(longTimeoutMillis, MILLISECONDS, executor); + } long startTime = System.nanoTime(); - CompletableFuture f = CompletableFuture.supplyAsync(() -> 1, d); - assertNull(f.getNow(null)); - try { - f.get(LONG_DELAY_MS, MILLISECONDS); - } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) > timeoutMillis/2); - checkCompletedNormally(f, 1); - } + CompletableFuture f = + CompletableFuture.supplyAsync(() -> v, delayer); + CompletableFuture g = + CompletableFuture.supplyAsync(() -> v, longDelayer); + + assertNull(g.getNow(null)); + + assertSame(v, f.get(LONG_DELAY_MS, MILLISECONDS)); + long millisElapsed = millisElapsedSince(startTime); + assertTrue(millisElapsed >= timeoutMillis); + assertTrue(millisElapsed < LONG_DELAY_MS / 2); - /** - * delayedExecutor for a given executor returns an executor that - * delays submission - */ - public void testDelayedExecutor2() { - long timeoutMillis = SMALL_DELAY_MS; - Executor d = CompletableFuture.delayedExecutor(timeoutMillis, - MILLISECONDS, - new ThreadExecutor()); - long startTime = System.nanoTime(); - CompletableFuture f = CompletableFuture.supplyAsync(() -> 1, d); - assertNull(f.getNow(null)); - try { - f.get(LONG_DELAY_MS, MILLISECONDS); - } catch (Throwable fail) { threadUnexpectedException(fail); } - assertTrue(millisElapsedSince(startTime) > timeoutMillis/2); - checkCompletedNormally(f, 1); + checkCompletedNormally(f, v); + + checkIncomplete(g); + assertTrue(g.cancel(true)); } //--- tests of implementation details; not part of official tck --- @@ -3707,4 +3697,91 @@ public class CompletableFutureTest exten } }} + /** + * Minimal completion stages throw UOE for all non-CompletionStage methods + */ + public void testMinimalCompletionStage_minimality() { + if (!testImplementationDetails) return; + Function toSignature = + (method) -> method.getName() + Arrays.toString(method.getParameterTypes()); + Predicate isNotStatic = + (method) -> (method.getModifiers() & Modifier.STATIC) == 0; + List minimalMethods = + Stream.of(Object.class, CompletionStage.class) + .flatMap((klazz) -> Stream.of(klazz.getMethods())) + .filter(isNotStatic) + .collect(Collectors.toList()); + // Methods from CompletableFuture permitted NOT to throw UOE + String[] signatureWhitelist = { + "newIncompleteFuture[]", + "defaultExecutor[]", + "minimalCompletionStage[]", + "copy[]", + }; + Set permittedMethodSignatures = + Stream.concat(minimalMethods.stream().map(toSignature), + Stream.of(signatureWhitelist)) + .collect(Collectors.toSet()); + List allMethods = Stream.of(CompletableFuture.class.getMethods()) + .filter(isNotStatic) + .filter((method) -> !permittedMethodSignatures.contains(toSignature.apply(method))) + .collect(Collectors.toList()); + + CompletionStage minimalStage = + new CompletableFuture().minimalCompletionStage(); + + List bugs = new ArrayList<>(); + for (Method method : allMethods) { + Class[] parameterTypes = method.getParameterTypes(); + Object[] args = new Object[parameterTypes.length]; + // Manufacture boxed primitives for primitive params + for (int i = 0; i < args.length; i++) { + Class type = parameterTypes[i]; + if (parameterTypes[i] == boolean.class) + args[i] = false; + else if (parameterTypes[i] == int.class) + args[i] = 0; + else if (parameterTypes[i] == long.class) + args[i] = 0L; + } + try { + method.invoke(minimalStage, args); + bugs.add(method); + } + catch (java.lang.reflect.InvocationTargetException expected) { + if (! (expected.getCause() instanceof UnsupportedOperationException)) { + bugs.add(method); + // expected.getCause().printStackTrace(); + } + } + catch (ReflectiveOperationException bad) { throw new Error(bad); } + } + if (!bugs.isEmpty()) + throw new Error("Methods did not throw UOE: " + bugs.toString()); + } + +// static U join(CompletionStage stage) { +// CompletableFuture f = new CompletableFuture<>(); +// stage.whenComplete((v, ex) -> { +// if (ex != null) f.completeExceptionally(ex); else f.complete(v); +// }); +// return f.join(); +// } + +// static boolean isDone(CompletionStage stage) { +// CompletableFuture f = new CompletableFuture<>(); +// stage.whenComplete((v, ex) -> { +// if (ex != null) f.completeExceptionally(ex); else f.complete(v); +// }); +// return f.isDone(); +// } + +// static U join2(CompletionStage stage) { +// return stage.toCompletableFuture().copy().join(); +// } + +// static boolean isDone2(CompletionStage stage) { +// return stage.toCompletableFuture().copy().isDone(); +// } + }