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Comparing jsr166/src/test/tck/CompletableFutureTest.java (file contents):
Revision 1.121 by jsr166, Sun Sep 6 21:14:12 2015 UTC vs.
Revision 1.149 by jsr166, Sun Jun 26 16:01:17 2016 UTC

#	Line 7 | Line 7
7
8		import static java.util.concurrent.TimeUnit.MILLISECONDS;
9		import static java.util.concurrent.TimeUnit.SECONDS;
10	+	import static java.util.concurrent.CompletableFuture.completedFuture;
11	+	import static java.util.concurrent.CompletableFuture.failedFuture;
12	+
13	+	import java.lang.reflect.Method;
14	+	import java.lang.reflect.Modifier;
15	+
16	+	import java.util.stream.Collectors;
17	+	import java.util.stream.Stream;
18
19		import java.util.ArrayList;
20	+	import java.util.Arrays;
21		import java.util.List;
22		import java.util.Objects;
23	+	import java.util.Set;
24		import java.util.concurrent.Callable;
25		import java.util.concurrent.CancellationException;
26		import java.util.concurrent.CompletableFuture;
#	Line 28 | Line 38 | import java.util.function.BiConsumer;
38		import java.util.function.BiFunction;
39		import java.util.function.Consumer;
40		import java.util.function.Function;
41	+	import java.util.function.Predicate;
42		import java.util.function.Supplier;
43
44	+	import junit.framework.AssertionFailedError;
45		import junit.framework.Test;
46		import junit.framework.TestSuite;
47
#	Line 828 | Line 840 | public class CompletableFutureTest exten
840		if (!createIncomplete) assertTrue(f.complete(v1));
841		final CompletableFuture<Integer> g = f.exceptionally
842		((Throwable t) -> {
831	–	// Should not be called
843		a.getAndIncrement();
844	<	throw new AssertionError();
844	>	threadFail("should not be called");
845	>	return null;            // unreached
846		});
847		if (createIncomplete) assertTrue(f.complete(v1));
848
#	Line 864 | Line 876 | public class CompletableFutureTest exten
876		assertEquals(1, a.get());
877		}}
878
879	+	/**
880	+	* If an "exceptionally action" throws an exception, it completes
881	+	* exceptionally with that exception
882	+	*/
883		public void testExceptionally_exceptionalCompletionActionFailed() {
884		for (boolean createIncomplete : new boolean[] { true, false })
885		{
#	Line 882 | Line 898 | public class CompletableFutureTest exten
898		if (createIncomplete) f.completeExceptionally(ex1);
899
900		checkCompletedWithWrappedException(g, ex2);
901	+	checkCompletedExceptionally(f, ex1);
902		assertEquals(1, a.get());
903		}}
904
#	Line 889 | Line 906 | public class CompletableFutureTest exten
906		* whenComplete action executes on normal completion, propagating
907		* source result.
908		*/
909	<	public void testWhenComplete_normalCompletion1() {
909	>	public void testWhenComplete_normalCompletion() {
910		for (ExecutionMode m : ExecutionMode.values())
911		for (boolean createIncomplete : new boolean[] { true, false })
912		for (Integer v1 : new Integer[] { 1, null })
#	Line 899 | Line 916 | public class CompletableFutureTest exten
916		if (!createIncomplete) assertTrue(f.complete(v1));
917		final CompletableFuture<Integer> g = m.whenComplete
918		(f,
919	<	(Integer x, Throwable t) -> {
919	>	(Integer result, Throwable t) -> {
920		m.checkExecutionMode();
921	<	threadAssertSame(x, v1);
921	>	threadAssertSame(result, v1);
922		threadAssertNull(t);
923		a.getAndIncrement();
924		});
#	Line 926 | Line 943 | public class CompletableFutureTest exten
943		if (!createIncomplete) f.completeExceptionally(ex);
944		final CompletableFuture<Integer> g = m.whenComplete
945		(f,
946	<	(Integer x, Throwable t) -> {
946	>	(Integer result, Throwable t) -> {
947		m.checkExecutionMode();
948	<	threadAssertNull(x);
948	>	threadAssertNull(result);
949		threadAssertSame(t, ex);
950		a.getAndIncrement();
951		});
#	Line 953 | Line 970 | public class CompletableFutureTest exten
970		if (!createIncomplete) assertTrue(f.cancel(mayInterruptIfRunning));
971		final CompletableFuture<Integer> g = m.whenComplete
972		(f,
973	<	(Integer x, Throwable t) -> {
973	>	(Integer result, Throwable t) -> {
974		m.checkExecutionMode();
975	<	threadAssertNull(x);
975	>	threadAssertNull(result);
976		threadAssertTrue(t instanceof CancellationException);
977		a.getAndIncrement();
978		});
#	Line 970 | Line 987 | public class CompletableFutureTest exten
987		* If a whenComplete action throws an exception when triggered by
988		* a normal completion, it completes exceptionally
989		*/
990	<	public void testWhenComplete_actionFailed() {
990	>	public void testWhenComplete_sourceCompletedNormallyActionFailed() {
991		for (boolean createIncomplete : new boolean[] { true, false })
992		for (ExecutionMode m : ExecutionMode.values())
993		for (Integer v1 : new Integer[] { 1, null })
#	Line 981 | Line 998 | public class CompletableFutureTest exten
998		if (!createIncomplete) assertTrue(f.complete(v1));
999		final CompletableFuture<Integer> g = m.whenComplete
1000		(f,
1001	<	(Integer x, Throwable t) -> {
1001	>	(Integer result, Throwable t) -> {
1002		m.checkExecutionMode();
1003	<	threadAssertSame(x, v1);
1003	>	threadAssertSame(result, v1);
1004		threadAssertNull(t);
1005		a.getAndIncrement();
1006		throw ex;
#	Line 998 | Line 1015 | public class CompletableFutureTest exten
1015		/**
1016		* If a whenComplete action throws an exception when triggered by
1017		* a source completion that also throws an exception, the source
1018	<	* exception takes precedence.
1018	>	* exception takes precedence (unlike handle)
1019		*/
1020	<	public void testWhenComplete_actionFailedSourceFailed() {
1020	>	public void testWhenComplete_sourceFailedActionFailed() {
1021		for (boolean createIncomplete : new boolean[] { true, false })
1022		for (ExecutionMode m : ExecutionMode.values())
1023		{
#	Line 1012 | Line 1029 | public class CompletableFutureTest exten
1029		if (!createIncomplete) f.completeExceptionally(ex1);
1030		final CompletableFuture<Integer> g = m.whenComplete
1031		(f,
1032	<	(Integer x, Throwable t) -> {
1032	>	(Integer result, Throwable t) -> {
1033		m.checkExecutionMode();
1034		threadAssertSame(t, ex1);
1035	<	threadAssertNull(x);
1035	>	threadAssertNull(result);
1036		a.getAndIncrement();
1037		throw ex2;
1038		});
#	Line 1023 | Line 1040 | public class CompletableFutureTest exten
1040
1041		checkCompletedWithWrappedException(g, ex1);
1042		checkCompletedExceptionally(f, ex1);
1043	+	if (testImplementationDetails) {
1044	+	assertEquals(1, ex1.getSuppressed().length);
1045	+	assertSame(ex2, ex1.getSuppressed()[0]);
1046	+	}
1047		assertEquals(1, a.get());
1048		}}
1049
#	Line 1040 | Line 1061 | public class CompletableFutureTest exten
1061		if (!createIncomplete) assertTrue(f.complete(v1));
1062		final CompletableFuture<Integer> g = m.handle
1063		(f,
1064	<	(Integer x, Throwable t) -> {
1064	>	(Integer result, Throwable t) -> {
1065		m.checkExecutionMode();
1066	<	threadAssertSame(x, v1);
1066	>	threadAssertSame(result, v1);
1067		threadAssertNull(t);
1068		a.getAndIncrement();
1069		return inc(v1);
#	Line 1069 | Line 1090 | public class CompletableFutureTest exten
1090		if (!createIncomplete) f.completeExceptionally(ex);
1091		final CompletableFuture<Integer> g = m.handle
1092		(f,
1093	<	(Integer x, Throwable t) -> {
1093	>	(Integer result, Throwable t) -> {
1094		m.checkExecutionMode();
1095	<	threadAssertNull(x);
1095	>	threadAssertNull(result);
1096		threadAssertSame(t, ex);
1097		a.getAndIncrement();
1098		return v1;
#	Line 1098 | Line 1119 | public class CompletableFutureTest exten
1119		if (!createIncomplete) assertTrue(f.cancel(mayInterruptIfRunning));
1120		final CompletableFuture<Integer> g = m.handle
1121		(f,
1122	<	(Integer x, Throwable t) -> {
1122	>	(Integer result, Throwable t) -> {
1123		m.checkExecutionMode();
1124	<	threadAssertNull(x);
1124	>	threadAssertNull(result);
1125		threadAssertTrue(t instanceof CancellationException);
1126		a.getAndIncrement();
1127		return v1;
#	Line 1113 | Line 1134 | public class CompletableFutureTest exten
1134		}}
1135
1136		/**
1137	<	* handle result completes exceptionally if action does
1137	>	* If a "handle action" throws an exception when triggered by
1138	>	* a normal completion, it completes exceptionally
1139		*/
1140	<	public void testHandle_sourceFailedActionFailed() {
1140	>	public void testHandle_sourceCompletedNormallyActionFailed() {
1141		for (ExecutionMode m : ExecutionMode.values())
1142		for (boolean createIncomplete : new boolean[] { true, false })
1143	+	for (Integer v1 : new Integer[] { 1, null })
1144		{
1145		final CompletableFuture<Integer> f = new CompletableFuture<>();
1146		final AtomicInteger a = new AtomicInteger(0);
1147	<	final CFException ex1 = new CFException();
1148	<	final CFException ex2 = new CFException();
1126	<	if (!createIncomplete) f.completeExceptionally(ex1);
1147	>	final CFException ex = new CFException();
1148	>	if (!createIncomplete) assertTrue(f.complete(v1));
1149		final CompletableFuture<Integer> g = m.handle
1150		(f,
1151	<	(Integer x, Throwable t) -> {
1151	>	(Integer result, Throwable t) -> {
1152		m.checkExecutionMode();
1153	<	threadAssertNull(x);
1154	<	threadAssertSame(ex1, t);
1153	>	threadAssertSame(result, v1);
1154	>	threadAssertNull(t);
1155		a.getAndIncrement();
1156	<	throw ex2;
1156	>	throw ex;
1157		});
1158	<	if (createIncomplete) f.completeExceptionally(ex1);
1158	>	if (createIncomplete) assertTrue(f.complete(v1));
1159
1160	<	checkCompletedWithWrappedException(g, ex2);
1161	<	checkCompletedExceptionally(f, ex1);
1160	>	checkCompletedWithWrappedException(g, ex);
1161	>	checkCompletedNormally(f, v1);
1162		assertEquals(1, a.get());
1163		}}
1164
1165	<	public void testHandle_sourceCompletedNormallyActionFailed() {
1166	<	for (ExecutionMode m : ExecutionMode.values())
1165	>	/**
1166	>	* If a "handle action" throws an exception when triggered by
1167	>	* a source completion that also throws an exception, the action
1168	>	* exception takes precedence (unlike whenComplete)
1169	>	*/
1170	>	public void testHandle_sourceFailedActionFailed() {
1171		for (boolean createIncomplete : new boolean[] { true, false })
1172	<	for (Integer v1 : new Integer[] { 1, null })
1172	>	for (ExecutionMode m : ExecutionMode.values())
1173		{
1148	–	final CompletableFuture<Integer> f = new CompletableFuture<>();
1174		final AtomicInteger a = new AtomicInteger(0);
1175	<	final CFException ex = new CFException();
1176	<	if (!createIncomplete) assertTrue(f.complete(v1));
1175	>	final CFException ex1 = new CFException();
1176	>	final CFException ex2 = new CFException();
1177	>	final CompletableFuture<Integer> f = new CompletableFuture<>();
1178	>
1179	>	if (!createIncomplete) f.completeExceptionally(ex1);
1180		final CompletableFuture<Integer> g = m.handle
1181		(f,
1182	<	(Integer x, Throwable t) -> {
1182	>	(Integer result, Throwable t) -> {
1183		m.checkExecutionMode();
1184	<	threadAssertSame(x, v1);
1185	<	threadAssertNull(t);
1184	>	threadAssertNull(result);
1185	>	threadAssertSame(ex1, t);
1186		a.getAndIncrement();
1187	<	throw ex;
1187	>	throw ex2;
1188		});
1189	<	if (createIncomplete) assertTrue(f.complete(v1));
1189	>	if (createIncomplete) f.completeExceptionally(ex1);
1190
1191	<	checkCompletedWithWrappedException(g, ex);
1192	<	checkCompletedNormally(f, v1);
1191	>	checkCompletedWithWrappedException(g, ex2);
1192	>	checkCompletedExceptionally(f, ex1);
1193		assertEquals(1, a.get());
1194		}}
1195
#	Line 3267 | Line 3295 | public class CompletableFutureTest exten
3295		() -> f.obtrudeException(null),
3296
3297		() -> CompletableFuture.delayedExecutor(1L, SECONDS, null),
3298	<	() -> CompletableFuture.delayedExecutor(1L, null, new ThreadExecutor()),
3298	>	() -> CompletableFuture.delayedExecutor(1L, null, exec),
3299		() -> CompletableFuture.delayedExecutor(1L, null),
3300
3301		() -> f.orTimeout(1L, null),
#	Line 3497 | Line 3525 | public class CompletableFutureTest exten
3525		long timeoutMillis = timeoutMillis();
3526		CompletableFuture<Integer> f = new CompletableFuture<>();
3527		long startTime = System.nanoTime();
3528	<	f.orTimeout(timeoutMillis, MILLISECONDS);
3528	>	assertSame(f, f.orTimeout(timeoutMillis, MILLISECONDS));
3529		checkCompletedWithTimeoutException(f);
3530		assertTrue(millisElapsedSince(startTime) >= timeoutMillis);
3531		}
#	Line 3512 | Line 3540 | public class CompletableFutureTest exten
3540		CompletableFuture<Integer> g = new CompletableFuture<>();
3541		long startTime = System.nanoTime();
3542		f.complete(v1);
3543	<	f.orTimeout(LONG_DELAY_MS, MILLISECONDS);
3544	<	g.orTimeout(LONG_DELAY_MS, MILLISECONDS);
3543	>	assertSame(f, f.orTimeout(LONG_DELAY_MS, MILLISECONDS));
3544	>	assertSame(g, g.orTimeout(LONG_DELAY_MS, MILLISECONDS));
3545		g.complete(v1);
3546		checkCompletedNormally(f, v1);
3547		checkCompletedNormally(g, v1);
#	Line 3528 | Line 3556 | public class CompletableFutureTest exten
3556		() -> testCompleteOnTimeout_timesOut(null));
3557		}
3558
3559	+	/**
3560	+	* completeOnTimeout completes with given value if not complete
3561	+	*/
3562		public void testCompleteOnTimeout_timesOut(Integer v) {
3563		long timeoutMillis = timeoutMillis();
3564		CompletableFuture<Integer> f = new CompletableFuture<>();
3565		long startTime = System.nanoTime();
3566	<	f.completeOnTimeout(v, timeoutMillis, MILLISECONDS);
3566	>	assertSame(f, f.completeOnTimeout(v, timeoutMillis, MILLISECONDS));
3567		assertSame(v, f.join());
3568		assertTrue(millisElapsedSince(startTime) >= timeoutMillis);
3569		f.complete(99);         // should have no effect
#	Line 3549 | Line 3580 | public class CompletableFutureTest exten
3580		CompletableFuture<Integer> g = new CompletableFuture<>();
3581		long startTime = System.nanoTime();
3582		f.complete(v1);
3583	<	f.completeOnTimeout(-1, LONG_DELAY_MS, MILLISECONDS);
3584	<	g.completeOnTimeout(-1, LONG_DELAY_MS, MILLISECONDS);
3583	>	assertSame(f, f.completeOnTimeout(-1, LONG_DELAY_MS, MILLISECONDS));
3584	>	assertSame(g, g.completeOnTimeout(-1, LONG_DELAY_MS, MILLISECONDS));
3585		g.complete(v1);
3586		checkCompletedNormally(f, v1);
3587		checkCompletedNormally(g, v1);
#	Line 3567 | Line 3598 | public class CompletableFutureTest exten
3598		() -> testDelayedExecutor(new ThreadExecutor(), 1));
3599		}
3600
3570	–	/**
3571	–	* delayedExecutor returns an executor that delays submission
3572	–	*/
3601		public void testDelayedExecutor(Executor executor, Integer v) throws Exception {
3602		long timeoutMillis = timeoutMillis();
3603		// Use an "unreasonably long" long timeout to catch lingering threads
#	Line 3604 | Line 3632 | public class CompletableFutureTest exten
3632		//--- tests of implementation details; not part of official tck ---
3633
3634		Object resultOf(CompletableFuture<?> f) {
3635	+	SecurityManager sm = System.getSecurityManager();
3636	+	if (sm != null) {
3637	+	try {
3638	+	System.setSecurityManager(null);
3639	+	} catch (SecurityException giveUp) {
3640	+	return "Reflection not available";
3641	+	}
3642	+	}
3643	+
3644		try {
3645		java.lang.reflect.Field resultField
3646		= CompletableFuture.class.getDeclaredField("result");
3647		resultField.setAccessible(true);
3648		return resultField.get(f);
3649	<	} catch (Throwable t) { throw new AssertionError(t); }
3649	>	} catch (Throwable t) {
3650	>	throw new AssertionError(t);
3651	>	} finally {
3652	>	if (sm != null) System.setSecurityManager(sm);
3653	>	}
3654		}
3655
3656		public void testExceptionPropagationReusesResultObject() {
#	Line 3632 | Line 3673 | public class CompletableFutureTest exten
3673		funs.add((y) -> m.applyToEither(y, incomplete, new IncFunction(m)));
3674
3675		funs.add((y) -> m.runAfterBoth(y, v42, new Noop(m)));
3676	+	funs.add((y) -> m.runAfterBoth(v42, y, new Noop(m)));
3677		funs.add((y) -> m.thenAcceptBoth(y, v42, new SubtractAction(m)));
3678	+	funs.add((y) -> m.thenAcceptBoth(v42, y, new SubtractAction(m)));
3679		funs.add((y) -> m.thenCombine(y, v42, new SubtractFunction(m)));
3680	+	funs.add((y) -> m.thenCombine(v42, y, new SubtractFunction(m)));
3681
3682	<	funs.add((y) -> m.whenComplete(y, (Integer x, Throwable t) -> {}));
3682	>	funs.add((y) -> m.whenComplete(y, (Integer r, Throwable t) -> {}));
3683
3684		funs.add((y) -> m.thenCompose(y, new CompletableFutureInc(m)));
3685
3686	+	funs.add((y) -> CompletableFuture.allOf(new CompletableFuture<?>[] {y}));
3687		funs.add((y) -> CompletableFuture.allOf(new CompletableFuture<?>[] {y, v42}));
3688	+	funs.add((y) -> CompletableFuture.allOf(new CompletableFuture<?>[] {v42, y}));
3689	+	funs.add((y) -> CompletableFuture.anyOf(new CompletableFuture<?>[] {y}));
3690		funs.add((y) -> CompletableFuture.anyOf(new CompletableFuture<?>[] {y, incomplete}));
3691	+	funs.add((y) -> CompletableFuture.anyOf(new CompletableFuture<?>[] {incomplete, y}));
3692
3693		for (Function<CompletableFuture<Integer>, CompletableFuture<?>>
3694		fun : funs) {
#	Line 3691 | Line 3739 | public class CompletableFutureTest exten
3739		}
3740		}}
3741
3742	+	/**
3743	+	* Minimal completion stages throw UOE for all non-CompletionStage methods
3744	+	*/
3745	+	public void testMinimalCompletionStage_minimality() {
3746	+	if (!testImplementationDetails) return;
3747	+	Function<Method, String> toSignature =
3748	+	(method) -> method.getName() + Arrays.toString(method.getParameterTypes());
3749	+	Predicate<Method> isNotStatic =
3750	+	(method) -> (method.getModifiers() & Modifier.STATIC) == 0;
3751	+	List<Method> minimalMethods =
3752	+	Stream.of(Object.class, CompletionStage.class)
3753	+	.flatMap((klazz) -> Stream.of(klazz.getMethods()))
3754	+	.filter(isNotStatic)
3755	+	.collect(Collectors.toList());
3756	+	// Methods from CompletableFuture permitted NOT to throw UOE
3757	+	String[] signatureWhitelist = {
3758	+	"newIncompleteFuture[]",
3759	+	"defaultExecutor[]",
3760	+	"minimalCompletionStage[]",
3761	+	"copy[]",
3762	+	};
3763	+	Set<String> permittedMethodSignatures =
3764	+	Stream.concat(minimalMethods.stream().map(toSignature),
3765	+	Stream.of(signatureWhitelist))
3766	+	.collect(Collectors.toSet());
3767	+	List<Method> allMethods = Stream.of(CompletableFuture.class.getMethods())
3768	+	.filter(isNotStatic)
3769	+	.filter((method) -> !permittedMethodSignatures.contains(toSignature.apply(method)))
3770	+	.collect(Collectors.toList());
3771	+
3772	+	CompletionStage<Integer> minimalStage =
3773	+	new CompletableFuture<Integer>().minimalCompletionStage();
3774	+
3775	+	List<Method> bugs = new ArrayList<>();
3776	+	for (Method method : allMethods) {
3777	+	Class<?>[] parameterTypes = method.getParameterTypes();
3778	+	Object[] args = new Object[parameterTypes.length];
3779	+	// Manufacture boxed primitives for primitive params
3780	+	for (int i = 0; i < args.length; i++) {
3781	+	Class<?> type = parameterTypes[i];
3782	+	if (parameterTypes[i] == boolean.class)
3783	+	args[i] = false;
3784	+	else if (parameterTypes[i] == int.class)
3785	+	args[i] = 0;
3786	+	else if (parameterTypes[i] == long.class)
3787	+	args[i] = 0L;
3788	+	}
3789	+	try {
3790	+	method.invoke(minimalStage, args);
3791	+	bugs.add(method);
3792	+	}
3793	+	catch (java.lang.reflect.InvocationTargetException expected) {
3794	+	if (! (expected.getCause() instanceof UnsupportedOperationException)) {
3795	+	bugs.add(method);
3796	+	// expected.getCause().printStackTrace();
3797	+	}
3798	+	}
3799	+	catch (ReflectiveOperationException bad) { throw new Error(bad); }
3800	+	}
3801	+	if (!bugs.isEmpty())
3802	+	throw new Error("Methods did not throw UOE: " + bugs.toString());
3803	+	}
3804	+
3805	+	static class Monad {
3806	+	static class ZeroException extends RuntimeException {
3807	+	public ZeroException() { super("monadic zero"); }
3808	+	}
3809	+	// "return", "unit"
3810	+	static <T> CompletableFuture<T> unit(T value) {
3811	+	return completedFuture(value);
3812	+	}
3813	+	// monadic zero ?
3814	+	static <T> CompletableFuture<T> zero() {
3815	+	return failedFuture(new ZeroException());
3816	+	}
3817	+	// >=>
3818	+	static <T,U,V> Function<T, CompletableFuture<V>> compose
3819	+	(Function<T, CompletableFuture<U>> f,
3820	+	Function<U, CompletableFuture<V>> g) {
3821	+	return (x) -> f.apply(x).thenCompose(g);
3822	+	}
3823	+
3824	+	static void assertZero(CompletableFuture<?> f) {
3825	+	try {
3826	+	f.getNow(null);
3827	+	throw new AssertionFailedError("should throw");
3828	+	} catch (CompletionException success) {
3829	+	assertTrue(success.getCause() instanceof ZeroException);
3830	+	}
3831	+	}
3832	+
3833	+	static <T> void assertFutureEquals(CompletableFuture<T> f,
3834	+	CompletableFuture<T> g) {
3835	+	T fval = null, gval = null;
3836	+	Throwable fex = null, gex = null;
3837	+
3838	+	try { fval = f.get(); }
3839	+	catch (ExecutionException ex) { fex = ex.getCause(); }
3840	+	catch (Throwable ex) { fex = ex; }
3841	+
3842	+	try { gval = g.get(); }
3843	+	catch (ExecutionException ex) { gex = ex.getCause(); }
3844	+	catch (Throwable ex) { gex = ex; }
3845	+
3846	+	if (fex != null || gex != null)
3847	+	assertSame(fex.getClass(), gex.getClass());
3848	+	else
3849	+	assertEquals(fval, gval);
3850	+	}
3851	+
3852	+	static class PlusFuture<T> extends CompletableFuture<T> {
3853	+	AtomicReference<Throwable> firstFailure = new AtomicReference<>(null);
3854	+	}
3855	+
3856	+	/** Implements "monadic plus". */
3857	+	static <T> CompletableFuture<T> plus(CompletableFuture<? extends T> f,
3858	+	CompletableFuture<? extends T> g) {
3859	+	PlusFuture<T> plus = new PlusFuture<T>();
3860	+	BiConsumer<T, Throwable> action = (T result, Throwable ex) -> {
3861	+	try {
3862	+	if (ex == null) {
3863	+	if (plus.complete(result))
3864	+	if (plus.firstFailure.get() != null)
3865	+	plus.firstFailure.set(null);
3866	+	}
3867	+	else if (plus.firstFailure.compareAndSet(null, ex)) {
3868	+	if (plus.isDone())
3869	+	plus.firstFailure.set(null);
3870	+	}
3871	+	else {
3872	+	// first failure has precedence
3873	+	Throwable first = plus.firstFailure.getAndSet(null);
3874	+
3875	+	// may fail with "Self-suppression not permitted"
3876	+	try { first.addSuppressed(ex); }
3877	+	catch (Exception ignored) {}
3878	+
3879	+	plus.completeExceptionally(first);
3880	+	}
3881	+	} catch (Throwable unexpected) {
3882	+	plus.completeExceptionally(unexpected);
3883	+	}
3884	+	};
3885	+	f.whenComplete(action);
3886	+	g.whenComplete(action);
3887	+	return plus;
3888	+	}
3889	+	}
3890	+
3891	+	/**
3892	+	* CompletableFuture is an additive monad - sort of.
3893	+	* https://en.wikipedia.org/wiki/Monad_(functional_programming)#Additive_monads
3894	+	*/
3895	+	public void testAdditiveMonad() throws Throwable {
3896	+	Function<Long, CompletableFuture<Long>> unit = Monad::unit;
3897	+	CompletableFuture<Long> zero = Monad.zero();
3898	+
3899	+	// Some mutually non-commutative functions
3900	+	Function<Long, CompletableFuture<Long>> triple
3901	+	= (x) -> Monad.unit(3 * x);
3902	+	Function<Long, CompletableFuture<Long>> inc
3903	+	= (x) -> Monad.unit(x + 1);
3904	+
3905	+	// unit is a right identity: m >>= unit === m
3906	+	Monad.assertFutureEquals(inc.apply(5L).thenCompose(unit),
3907	+	inc.apply(5L));
3908	+	// unit is a left identity: (unit x) >>= f === f x
3909	+	Monad.assertFutureEquals(unit.apply(5L).thenCompose(inc),
3910	+	inc.apply(5L));
3911	+
3912	+	// associativity: (m >>= f) >>= g === m >>= ( \x -> (f x >>= g) )
3913	+	Monad.assertFutureEquals(
3914	+	unit.apply(5L).thenCompose(inc).thenCompose(triple),
3915	+	unit.apply(5L).thenCompose((x) -> inc.apply(x).thenCompose(triple)));
3916	+
3917	+	// The case for CompletableFuture as an additive monad is weaker...
3918	+
3919	+	// zero is a monadic zero
3920	+	Monad.assertZero(zero);
3921	+
3922	+	// left zero: zero >>= f === zero
3923	+	Monad.assertZero(zero.thenCompose(inc));
3924	+	// right zero: f >>= (\x -> zero) === zero
3925	+	Monad.assertZero(inc.apply(5L).thenCompose((x) -> zero));
3926	+
3927	+	// f plus zero === f
3928	+	Monad.assertFutureEquals(Monad.unit(5L),
3929	+	Monad.plus(Monad.unit(5L), zero));
3930	+	// zero plus f === f
3931	+	Monad.assertFutureEquals(Monad.unit(5L),
3932	+	Monad.plus(zero, Monad.unit(5L)));
3933	+	// zero plus zero === zero
3934	+	Monad.assertZero(Monad.plus(zero, zero));
3935	+	{
3936	+	CompletableFuture<Long> f = Monad.plus(Monad.unit(5L),
3937	+	Monad.unit(8L));
3938	+	// non-determinism
3939	+	assertTrue(f.get() == 5L || f.get() == 8L);
3940	+	}
3941	+
3942	+	CompletableFuture<Long> godot = new CompletableFuture<>();
3943	+	// f plus godot === f (doesn't wait for godot)
3944	+	Monad.assertFutureEquals(Monad.unit(5L),
3945	+	Monad.plus(Monad.unit(5L), godot));
3946	+	// godot plus f === f (doesn't wait for godot)
3947	+	Monad.assertFutureEquals(Monad.unit(5L),
3948	+	Monad.plus(godot, Monad.unit(5L)));
3949	+	}
3950	+
3951	+	/**
3952	+	* A single CompletableFuture with many dependents.
3953	+	* A demo of scalability - runtime is O(n).
3954	+	*/
3955	+	public void testManyDependents() throws Throwable {
3956	+	final int n = 1_000;
3957	+	final CompletableFuture<Void> head = new CompletableFuture<>();
3958	+	final CompletableFuture<Void> complete = CompletableFuture.completedFuture((Void)null);
3959	+	final AtomicInteger count = new AtomicInteger(0);
3960	+	for (int i = 0; i < n; i++) {
3961	+	head.thenRun(() -> count.getAndIncrement());
3962	+	head.thenAccept((x) -> count.getAndIncrement());
3963	+	head.thenApply((x) -> count.getAndIncrement());
3964	+
3965	+	head.runAfterBoth(complete, () -> count.getAndIncrement());
3966	+	head.thenAcceptBoth(complete, (x, y) -> count.getAndIncrement());
3967	+	head.thenCombine(complete, (x, y) -> count.getAndIncrement());
3968	+	complete.runAfterBoth(head, () -> count.getAndIncrement());
3969	+	complete.thenAcceptBoth(head, (x, y) -> count.getAndIncrement());
3970	+	complete.thenCombine(head, (x, y) -> count.getAndIncrement());
3971	+
3972	+	head.runAfterEither(new CompletableFuture<Void>(), () -> count.getAndIncrement());
3973	+	head.acceptEither(new CompletableFuture<Void>(), (x) -> count.getAndIncrement());
3974	+	head.applyToEither(new CompletableFuture<Void>(), (x) -> count.getAndIncrement());
3975	+	new CompletableFuture<Void>().runAfterEither(head, () -> count.getAndIncrement());
3976	+	new CompletableFuture<Void>().acceptEither(head, (x) -> count.getAndIncrement());
3977	+	new CompletableFuture<Void>().applyToEither(head, (x) -> count.getAndIncrement());
3978	+	}
3979	+	head.complete(null);
3980	+	assertEquals(5 * 3 * n, count.get());
3981	+	}
3982	+
3983	+	//     static <U> U join(CompletionStage<U> stage) {
3984	+	//         CompletableFuture<U> f = new CompletableFuture<>();
3985	+	//         stage.whenComplete((v, ex) -> {
3986	+	//             if (ex != null) f.completeExceptionally(ex); else f.complete(v);
3987	+	//         });
3988	+	//         return f.join();
3989	+	//     }
3990	+
3991	+	//     static <U> boolean isDone(CompletionStage<U> stage) {
3992	+	//         CompletableFuture<U> f = new CompletableFuture<>();
3993	+	//         stage.whenComplete((v, ex) -> {
3994	+	//             if (ex != null) f.completeExceptionally(ex); else f.complete(v);
3995	+	//         });
3996	+	//         return f.isDone();
3997	+	//     }
3998	+
3999	+	//     static <U> U join2(CompletionStage<U> stage) {
4000	+	//         return stage.toCompletableFuture().copy().join();
4001	+	//     }
4002	+
4003	+	//     static <U> boolean isDone2(CompletionStage<U> stage) {
4004	+	//         return stage.toCompletableFuture().copy().isDone();
4005	+	//     }
4006	+
4007		}

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