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Comparing jsr166/src/test/tck/CompletableFutureTest.java (file contents):
Revision 1.100 by jsr166, Thu Jan 15 18:34:19 2015 UTC vs.
Revision 1.147 by jsr166, Sat Jun 4 23:49:29 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 21 | Line 31 | import java.util.concurrent.Executor;
31   import java.util.concurrent.ForkJoinPool;
32   import java.util.concurrent.ForkJoinTask;
33   import java.util.concurrent.TimeoutException;
34 + import java.util.concurrent.TimeUnit;
35   import java.util.concurrent.atomic.AtomicInteger;
36 + import java.util.concurrent.atomic.AtomicReference;
37   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  
48   public class CompletableFutureTest extends JSR166TestCase {
49  
50      public static void main(String[] args) {
51 <        junit.textui.TestRunner.run(suite());
51 >        main(suite(), args);
52      }
53      public static Test suite() {
54          return new TestSuite(CompletableFutureTest.class);
# Line 45 | Line 59 | public class CompletableFutureTest exten
59      void checkIncomplete(CompletableFuture<?> f) {
60          assertFalse(f.isDone());
61          assertFalse(f.isCancelled());
62 <        assertTrue(f.toString().contains("[Not completed]"));
62 >        assertTrue(f.toString().contains("Not completed"));
63          try {
64              assertNull(f.getNow(null));
65          } catch (Throwable fail) { threadUnexpectedException(fail); }
# Line 75 | Line 89 | public class CompletableFutureTest exten
89          assertTrue(f.toString().contains("[Completed normally]"));
90      }
91  
92 <    void checkCompletedWithWrappedCFException(CompletableFuture<?> f) {
92 >    /**
93 >     * Returns the "raw" internal exceptional completion of f,
94 >     * without any additional wrapping with CompletionException.
95 >     */
96 >    <U> Throwable exceptionalCompletion(CompletableFuture<U> f) {
97 >        // handle (and whenComplete) can distinguish between "direct"
98 >        // and "wrapped" exceptional completion
99 >        return f.handle((U u, Throwable t) -> t).join();
100 >    }
101 >
102 >    void checkCompletedExceptionally(CompletableFuture<?> f,
103 >                                     boolean wrapped,
104 >                                     Consumer<Throwable> checker) {
105 >        Throwable cause = exceptionalCompletion(f);
106 >        if (wrapped) {
107 >            assertTrue(cause instanceof CompletionException);
108 >            cause = cause.getCause();
109 >        }
110 >        checker.accept(cause);
111 >
112          long startTime = System.nanoTime();
80        long timeoutMillis = LONG_DELAY_MS;
113          try {
114 <            f.get(timeoutMillis, MILLISECONDS);
114 >            f.get(LONG_DELAY_MS, MILLISECONDS);
115              shouldThrow();
116          } catch (ExecutionException success) {
117 <            assertTrue(success.getCause() instanceof CFException);
117 >            assertSame(cause, success.getCause());
118          } catch (Throwable fail) { threadUnexpectedException(fail); }
119 <        assertTrue(millisElapsedSince(startTime) < timeoutMillis/2);
119 >        assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2);
120  
121          try {
122              f.join();
123              shouldThrow();
124          } catch (CompletionException success) {
125 <            assertTrue(success.getCause() instanceof CFException);
126 <        }
125 >            assertSame(cause, success.getCause());
126 >        } catch (Throwable fail) { threadUnexpectedException(fail); }
127 >
128          try {
129              f.getNow(null);
130              shouldThrow();
131          } catch (CompletionException success) {
132 <            assertTrue(success.getCause() instanceof CFException);
133 <        }
132 >            assertSame(cause, success.getCause());
133 >        } catch (Throwable fail) { threadUnexpectedException(fail); }
134 >
135          try {
136              f.get();
137              shouldThrow();
138          } catch (ExecutionException success) {
139 <            assertTrue(success.getCause() instanceof CFException);
139 >            assertSame(cause, success.getCause());
140          } catch (Throwable fail) { threadUnexpectedException(fail); }
141 <        assertTrue(f.isDone());
141 >
142          assertFalse(f.isCancelled());
143 +        assertTrue(f.isDone());
144 +        assertTrue(f.isCompletedExceptionally());
145          assertTrue(f.toString().contains("[Completed exceptionally]"));
146      }
147  
148 <    <U> void checkCompletedExceptionallyWithRootCause(CompletableFuture<U> f,
149 <                                                      Throwable ex) {
150 <        long startTime = System.nanoTime();
151 <        long timeoutMillis = LONG_DELAY_MS;
116 <        try {
117 <            f.get(timeoutMillis, MILLISECONDS);
118 <            shouldThrow();
119 <        } catch (ExecutionException success) {
120 <            assertSame(ex, success.getCause());
121 <        } catch (Throwable fail) { threadUnexpectedException(fail); }
122 <        assertTrue(millisElapsedSince(startTime) < timeoutMillis/2);
148 >    void checkCompletedWithWrappedCFException(CompletableFuture<?> f) {
149 >        checkCompletedExceptionally(f, true,
150 >            (t) -> assertTrue(t instanceof CFException));
151 >    }
152  
153 <        try {
154 <            f.join();
155 <            shouldThrow();
156 <        } catch (CompletionException success) {
128 <            assertSame(ex, success.getCause());
129 <        }
130 <        try {
131 <            f.getNow(null);
132 <            shouldThrow();
133 <        } catch (CompletionException success) {
134 <            assertSame(ex, success.getCause());
135 <        }
136 <        try {
137 <            f.get();
138 <            shouldThrow();
139 <        } catch (ExecutionException success) {
140 <            assertSame(ex, success.getCause());
141 <        } catch (Throwable fail) { threadUnexpectedException(fail); }
153 >    void checkCompletedWithWrappedCancellationException(CompletableFuture<?> f) {
154 >        checkCompletedExceptionally(f, true,
155 >            (t) -> assertTrue(t instanceof CancellationException));
156 >    }
157  
158 <        assertTrue(f.isDone());
159 <        assertFalse(f.isCancelled());
160 <        assertTrue(f.toString().contains("[Completed exceptionally]"));
158 >    void checkCompletedWithTimeoutException(CompletableFuture<?> f) {
159 >        checkCompletedExceptionally(f, false,
160 >            (t) -> assertTrue(t instanceof TimeoutException));
161      }
162  
163 <    <U> void checkCompletedWithWrappedException(CompletableFuture<U> f,
164 <                                                Throwable ex) {
165 <        checkCompletedExceptionallyWithRootCause(f, ex);
151 <        try {
152 <            CompletableFuture<Throwable> spy = f.handle
153 <                ((U u, Throwable t) -> t);
154 <            assertTrue(spy.join() instanceof CompletionException);
155 <            assertSame(ex, spy.join().getCause());
156 <        } catch (Throwable fail) { threadUnexpectedException(fail); }
163 >    void checkCompletedWithWrappedException(CompletableFuture<?> f,
164 >                                            Throwable ex) {
165 >        checkCompletedExceptionally(f, true, (t) -> assertSame(t, ex));
166      }
167  
168 <    <U> void checkCompletedExceptionally(CompletableFuture<U> f, Throwable ex) {
169 <        checkCompletedExceptionallyWithRootCause(f, ex);
161 <        try {
162 <            CompletableFuture<Throwable> spy = f.handle
163 <                ((U u, Throwable t) -> t);
164 <            assertSame(ex, spy.join());
165 <        } catch (Throwable fail) { threadUnexpectedException(fail); }
168 >    void checkCompletedExceptionally(CompletableFuture<?> f, Throwable ex) {
169 >        checkCompletedExceptionally(f, false, (t) -> assertSame(t, ex));
170      }
171  
172      void checkCancelled(CompletableFuture<?> f) {
173          long startTime = System.nanoTime();
170        long timeoutMillis = LONG_DELAY_MS;
174          try {
175 <            f.get(timeoutMillis, MILLISECONDS);
175 >            f.get(LONG_DELAY_MS, MILLISECONDS);
176              shouldThrow();
177          } catch (CancellationException success) {
178          } catch (Throwable fail) { threadUnexpectedException(fail); }
179 <        assertTrue(millisElapsedSince(startTime) < timeoutMillis/2);
179 >        assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2);
180  
181          try {
182              f.join();
# Line 188 | Line 191 | public class CompletableFutureTest exten
191              shouldThrow();
192          } catch (CancellationException success) {
193          } catch (Throwable fail) { threadUnexpectedException(fail); }
191        assertTrue(f.isDone());
192        assertTrue(f.isCompletedExceptionally());
193        assertTrue(f.isCancelled());
194        assertTrue(f.toString().contains("[Completed exceptionally]"));
195    }
194  
195 <    void checkCompletedWithWrappedCancellationException(CompletableFuture<?> f) {
198 <        long startTime = System.nanoTime();
199 <        long timeoutMillis = LONG_DELAY_MS;
200 <        try {
201 <            f.get(timeoutMillis, MILLISECONDS);
202 <            shouldThrow();
203 <        } catch (ExecutionException success) {
204 <            assertTrue(success.getCause() instanceof CancellationException);
205 <        } catch (Throwable fail) { threadUnexpectedException(fail); }
206 <        assertTrue(millisElapsedSince(startTime) < timeoutMillis/2);
195 >        assertTrue(exceptionalCompletion(f) instanceof CancellationException);
196  
208        try {
209            f.join();
210            shouldThrow();
211        } catch (CompletionException success) {
212            assertTrue(success.getCause() instanceof CancellationException);
213        }
214        try {
215            f.getNow(null);
216            shouldThrow();
217        } catch (CompletionException success) {
218            assertTrue(success.getCause() instanceof CancellationException);
219        }
220        try {
221            f.get();
222            shouldThrow();
223        } catch (ExecutionException success) {
224            assertTrue(success.getCause() instanceof CancellationException);
225        } catch (Throwable fail) { threadUnexpectedException(fail); }
197          assertTrue(f.isDone());
227        assertFalse(f.isCancelled());
198          assertTrue(f.isCompletedExceptionally());
199 +        assertTrue(f.isCancelled());
200          assertTrue(f.toString().contains("[Completed exceptionally]"));
201      }
202  
# Line 273 | Line 244 | public class CompletableFutureTest exten
244      {
245          CompletableFuture<Integer> f = new CompletableFuture<>();
246          checkIncomplete(f);
247 <        assertTrue(f.cancel(true));
248 <        assertTrue(f.cancel(true));
247 >        assertTrue(f.cancel(mayInterruptIfRunning));
248 >        assertTrue(f.cancel(mayInterruptIfRunning));
249 >        assertTrue(f.cancel(!mayInterruptIfRunning));
250          checkCancelled(f);
251      }}
252  
# Line 868 | Line 840 | public class CompletableFutureTest exten
840          if (!createIncomplete) assertTrue(f.complete(v1));
841          final CompletableFuture<Integer> g = f.exceptionally
842              ((Throwable t) -> {
871                // 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 904 | 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 })
909        for (Integer v1 : new Integer[] { 1, null })
885      {
886          final AtomicInteger a = new AtomicInteger(0);
887          final CFException ex1 = new CFException();
# Line 923 | 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 930 | 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 940 | 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 960 | Line 936 | public class CompletableFutureTest exten
936      public void testWhenComplete_exceptionalCompletion() {
937          for (ExecutionMode m : ExecutionMode.values())
938          for (boolean createIncomplete : new boolean[] { true, false })
963        for (Integer v1 : new Integer[] { 1, null })
939      {
940          final AtomicInteger a = new AtomicInteger(0);
941          final CFException ex = new CFException();
# Line 968 | 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 995 | 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 1012 | 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 1023 | 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 1040 | 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())
1048        for (Integer v1 : new Integer[] { 1, null })
1023      {
1024          final AtomicInteger a = new AtomicInteger(0);
1025          final CFException ex1 = new CFException();
# Line 1055 | 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 1066 | 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 1083 | 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 1112 | 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 1141 | 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 1156 | 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();
1169 <        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      {
1191        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 3105 | Line 3090 | public class CompletableFutureTest exten
3090              for (int i = 0; i < k; i++) {
3091                  checkIncomplete(f);
3092                  checkIncomplete(CompletableFuture.allOf(fs));
3093 <                if (i != k/2) {
3093 >                if (i != k / 2) {
3094                      fs[i].complete(i);
3095                      checkCompletedNormally(fs[i], i);
3096                  } else {
# Line 3212 | Line 3197 | public class CompletableFutureTest exten
3197          CompletableFuture<Integer> f = new CompletableFuture<>();
3198          CompletableFuture<Integer> g = new CompletableFuture<>();
3199          CompletableFuture<Integer> nullFuture = (CompletableFuture<Integer>)null;
3215        CompletableFuture<?> h;
3200          ThreadExecutor exec = new ThreadExecutor();
3201  
3202          Runnable[] throwingActions = {
# Line 3309 | Line 3293 | public class CompletableFutureTest exten
3293              () -> CompletableFuture.anyOf(null, f),
3294  
3295              () -> f.obtrudeException(null),
3296 +
3297 +            () -> CompletableFuture.delayedExecutor(1L, SECONDS, null),
3298 +            () -> CompletableFuture.delayedExecutor(1L, null, exec),
3299 +            () -> CompletableFuture.delayedExecutor(1L, null),
3300 +
3301 +            () -> f.orTimeout(1L, null),
3302 +            () -> f.completeOnTimeout(42, 1L, null),
3303 +
3304 +            () -> CompletableFuture.failedFuture(null),
3305 +            () -> CompletableFuture.failedStage(null),
3306          };
3307  
3308          assertThrows(NullPointerException.class, throwingActions);
# Line 3323 | Line 3317 | public class CompletableFutureTest exten
3317          assertSame(f, f.toCompletableFuture());
3318      }
3319  
3320 +    // jdk9
3321 +
3322 +    /**
3323 +     * newIncompleteFuture returns an incomplete CompletableFuture
3324 +     */
3325 +    public void testNewIncompleteFuture() {
3326 +        for (Integer v1 : new Integer[] { 1, null })
3327 +    {
3328 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3329 +        CompletableFuture<Integer> g = f.newIncompleteFuture();
3330 +        checkIncomplete(f);
3331 +        checkIncomplete(g);
3332 +        f.complete(v1);
3333 +        checkCompletedNormally(f, v1);
3334 +        checkIncomplete(g);
3335 +        g.complete(v1);
3336 +        checkCompletedNormally(g, v1);
3337 +        assertSame(g.getClass(), CompletableFuture.class);
3338 +    }}
3339 +
3340 +    /**
3341 +     * completedStage returns a completed CompletionStage
3342 +     */
3343 +    public void testCompletedStage() {
3344 +        AtomicInteger x = new AtomicInteger(0);
3345 +        AtomicReference<Throwable> r = new AtomicReference<Throwable>();
3346 +        CompletionStage<Integer> f = CompletableFuture.completedStage(1);
3347 +        f.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);});
3348 +        assertEquals(x.get(), 1);
3349 +        assertNull(r.get());
3350 +    }
3351 +
3352 +    /**
3353 +     * defaultExecutor by default returns the commonPool if
3354 +     * it supports more than one thread.
3355 +     */
3356 +    public void testDefaultExecutor() {
3357 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3358 +        Executor e = f.defaultExecutor();
3359 +        Executor c = ForkJoinPool.commonPool();
3360 +        if (ForkJoinPool.getCommonPoolParallelism() > 1)
3361 +            assertSame(e, c);
3362 +        else
3363 +            assertNotSame(e, c);
3364 +    }
3365 +
3366 +    /**
3367 +     * failedFuture returns a CompletableFuture completed
3368 +     * exceptionally with the given Exception
3369 +     */
3370 +    public void testFailedFuture() {
3371 +        CFException ex = new CFException();
3372 +        CompletableFuture<Integer> f = CompletableFuture.failedFuture(ex);
3373 +        checkCompletedExceptionally(f, ex);
3374 +    }
3375 +
3376 +    /**
3377 +     * failedFuture(null) throws NPE
3378 +     */
3379 +    public void testFailedFuture_null() {
3380 +        try {
3381 +            CompletableFuture<Integer> f = CompletableFuture.failedFuture(null);
3382 +            shouldThrow();
3383 +        } catch (NullPointerException success) {}
3384 +    }
3385 +
3386 +    /**
3387 +     * copy returns a CompletableFuture that is completed normally,
3388 +     * with the same value, when source is.
3389 +     */
3390 +    public void testCopy() {
3391 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3392 +        CompletableFuture<Integer> g = f.copy();
3393 +        checkIncomplete(f);
3394 +        checkIncomplete(g);
3395 +        f.complete(1);
3396 +        checkCompletedNormally(f, 1);
3397 +        checkCompletedNormally(g, 1);
3398 +    }
3399 +
3400 +    /**
3401 +     * copy returns a CompletableFuture that is completed exceptionally
3402 +     * when source is.
3403 +     */
3404 +    public void testCopy2() {
3405 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3406 +        CompletableFuture<Integer> g = f.copy();
3407 +        checkIncomplete(f);
3408 +        checkIncomplete(g);
3409 +        CFException ex = new CFException();
3410 +        f.completeExceptionally(ex);
3411 +        checkCompletedExceptionally(f, ex);
3412 +        checkCompletedWithWrappedException(g, ex);
3413 +    }
3414 +
3415 +    /**
3416 +     * minimalCompletionStage returns a CompletableFuture that is
3417 +     * completed normally, with the same value, when source is.
3418 +     */
3419 +    public void testMinimalCompletionStage() {
3420 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3421 +        CompletionStage<Integer> g = f.minimalCompletionStage();
3422 +        AtomicInteger x = new AtomicInteger(0);
3423 +        AtomicReference<Throwable> r = new AtomicReference<Throwable>();
3424 +        checkIncomplete(f);
3425 +        g.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);});
3426 +        f.complete(1);
3427 +        checkCompletedNormally(f, 1);
3428 +        assertEquals(x.get(), 1);
3429 +        assertNull(r.get());
3430 +    }
3431 +
3432 +    /**
3433 +     * minimalCompletionStage returns a CompletableFuture that is
3434 +     * completed exceptionally when source is.
3435 +     */
3436 +    public void testMinimalCompletionStage2() {
3437 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3438 +        CompletionStage<Integer> g = f.minimalCompletionStage();
3439 +        AtomicInteger x = new AtomicInteger(0);
3440 +        AtomicReference<Throwable> r = new AtomicReference<Throwable>();
3441 +        g.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);});
3442 +        checkIncomplete(f);
3443 +        CFException ex = new CFException();
3444 +        f.completeExceptionally(ex);
3445 +        checkCompletedExceptionally(f, ex);
3446 +        assertEquals(x.get(), 0);
3447 +        assertEquals(r.get().getCause(), ex);
3448 +    }
3449 +
3450 +    /**
3451 +     * failedStage returns a CompletionStage completed
3452 +     * exceptionally with the given Exception
3453 +     */
3454 +    public void testFailedStage() {
3455 +        CFException ex = new CFException();
3456 +        CompletionStage<Integer> f = CompletableFuture.failedStage(ex);
3457 +        AtomicInteger x = new AtomicInteger(0);
3458 +        AtomicReference<Throwable> r = new AtomicReference<Throwable>();
3459 +        f.whenComplete((v, e) -> {if (e != null) r.set(e); else x.set(v);});
3460 +        assertEquals(x.get(), 0);
3461 +        assertEquals(r.get(), ex);
3462 +    }
3463 +
3464 +    /**
3465 +     * completeAsync completes with value of given supplier
3466 +     */
3467 +    public void testCompleteAsync() {
3468 +        for (Integer v1 : new Integer[] { 1, null })
3469 +    {
3470 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3471 +        f.completeAsync(() -> v1);
3472 +        f.join();
3473 +        checkCompletedNormally(f, v1);
3474 +    }}
3475 +
3476 +    /**
3477 +     * completeAsync completes exceptionally if given supplier throws
3478 +     */
3479 +    public void testCompleteAsync2() {
3480 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3481 +        CFException ex = new CFException();
3482 +        f.completeAsync(() -> {if (true) throw ex; return 1;});
3483 +        try {
3484 +            f.join();
3485 +            shouldThrow();
3486 +        } catch (CompletionException success) {}
3487 +        checkCompletedWithWrappedException(f, ex);
3488 +    }
3489 +
3490 +    /**
3491 +     * completeAsync with given executor completes with value of given supplier
3492 +     */
3493 +    public void testCompleteAsync3() {
3494 +        for (Integer v1 : new Integer[] { 1, null })
3495 +    {
3496 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3497 +        ThreadExecutor executor = new ThreadExecutor();
3498 +        f.completeAsync(() -> v1, executor);
3499 +        assertSame(v1, f.join());
3500 +        checkCompletedNormally(f, v1);
3501 +        assertEquals(1, executor.count.get());
3502 +    }}
3503 +
3504 +    /**
3505 +     * completeAsync with given executor completes exceptionally if
3506 +     * given supplier throws
3507 +     */
3508 +    public void testCompleteAsync4() {
3509 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3510 +        CFException ex = new CFException();
3511 +        ThreadExecutor executor = new ThreadExecutor();
3512 +        f.completeAsync(() -> {if (true) throw ex; return 1;}, executor);
3513 +        try {
3514 +            f.join();
3515 +            shouldThrow();
3516 +        } catch (CompletionException success) {}
3517 +        checkCompletedWithWrappedException(f, ex);
3518 +        assertEquals(1, executor.count.get());
3519 +    }
3520 +
3521 +    /**
3522 +     * orTimeout completes with TimeoutException if not complete
3523 +     */
3524 +    public void testOrTimeout_timesOut() {
3525 +        long timeoutMillis = timeoutMillis();
3526 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3527 +        long startTime = System.nanoTime();
3528 +        assertSame(f, f.orTimeout(timeoutMillis, MILLISECONDS));
3529 +        checkCompletedWithTimeoutException(f);
3530 +        assertTrue(millisElapsedSince(startTime) >= timeoutMillis);
3531 +    }
3532 +
3533 +    /**
3534 +     * orTimeout completes normally if completed before timeout
3535 +     */
3536 +    public void testOrTimeout_completed() {
3537 +        for (Integer v1 : new Integer[] { 1, null })
3538 +    {
3539 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3540 +        CompletableFuture<Integer> g = new CompletableFuture<>();
3541 +        long startTime = System.nanoTime();
3542 +        f.complete(v1);
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);
3548 +        assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2);
3549 +    }}
3550 +
3551 +    /**
3552 +     * completeOnTimeout completes with given value if not complete
3553 +     */
3554 +    public void testCompleteOnTimeout_timesOut() {
3555 +        testInParallel(() -> testCompleteOnTimeout_timesOut(42),
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 +        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
3570 +        checkCompletedNormally(f, v);
3571 +    }
3572 +
3573 +    /**
3574 +     * completeOnTimeout has no effect if completed within timeout
3575 +     */
3576 +    public void testCompleteOnTimeout_completed() {
3577 +        for (Integer v1 : new Integer[] { 1, null })
3578 +    {
3579 +        CompletableFuture<Integer> f = new CompletableFuture<>();
3580 +        CompletableFuture<Integer> g = new CompletableFuture<>();
3581 +        long startTime = System.nanoTime();
3582 +        f.complete(v1);
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);
3588 +        assertTrue(millisElapsedSince(startTime) < LONG_DELAY_MS / 2);
3589 +    }}
3590 +
3591 +    /**
3592 +     * delayedExecutor returns an executor that delays submission
3593 +     */
3594 +    public void testDelayedExecutor() {
3595 +        testInParallel(() -> testDelayedExecutor(null, null),
3596 +                       () -> testDelayedExecutor(null, 1),
3597 +                       () -> testDelayedExecutor(new ThreadExecutor(), 1),
3598 +                       () -> testDelayedExecutor(new ThreadExecutor(), 1));
3599 +    }
3600 +
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
3604 +        long longTimeoutMillis = 1000 * 60 * 60 * 24;
3605 +        final Executor delayer, longDelayer;
3606 +        if (executor == null) {
3607 +            delayer = CompletableFuture.delayedExecutor(timeoutMillis, MILLISECONDS);
3608 +            longDelayer = CompletableFuture.delayedExecutor(longTimeoutMillis, MILLISECONDS);
3609 +        } else {
3610 +            delayer = CompletableFuture.delayedExecutor(timeoutMillis, MILLISECONDS, executor);
3611 +            longDelayer = CompletableFuture.delayedExecutor(longTimeoutMillis, MILLISECONDS, executor);
3612 +        }
3613 +        long startTime = System.nanoTime();
3614 +        CompletableFuture<Integer> f =
3615 +            CompletableFuture.supplyAsync(() -> v, delayer);
3616 +        CompletableFuture<Integer> g =
3617 +            CompletableFuture.supplyAsync(() -> v, longDelayer);
3618 +
3619 +        assertNull(g.getNow(null));
3620 +
3621 +        assertSame(v, f.get(LONG_DELAY_MS, MILLISECONDS));
3622 +        long millisElapsed = millisElapsedSince(startTime);
3623 +        assertTrue(millisElapsed >= timeoutMillis);
3624 +        assertTrue(millisElapsed < LONG_DELAY_MS / 2);
3625 +
3626 +        checkCompletedNormally(f, v);
3627 +
3628 +        checkIncomplete(g);
3629 +        assertTrue(g.cancel(true));
3630 +    }
3631 +
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 3357 | Line 3676 | public class CompletableFutureTest exten
3676          funs.add((y) -> m.thenAcceptBoth(y, v42, new SubtractAction(m)));
3677          funs.add((y) -> m.thenCombine(y, v42, new SubtractFunction(m)));
3678  
3679 <        funs.add((y) -> m.whenComplete(y, (Integer x, Throwable t) -> {}));
3679 >        funs.add((y) -> m.whenComplete(y, (Integer r, Throwable t) -> {}));
3680  
3681          funs.add((y) -> m.thenCompose(y, new CompletableFutureInc(m)));
3682  
# Line 3413 | Line 3732 | public class CompletableFutureTest exten
3732          }
3733      }}
3734  
3735 +    /**
3736 +     * Minimal completion stages throw UOE for all non-CompletionStage methods
3737 +     */
3738 +    public void testMinimalCompletionStage_minimality() {
3739 +        if (!testImplementationDetails) return;
3740 +        Function<Method, String> toSignature =
3741 +            (method) -> method.getName() + Arrays.toString(method.getParameterTypes());
3742 +        Predicate<Method> isNotStatic =
3743 +            (method) -> (method.getModifiers() & Modifier.STATIC) == 0;
3744 +        List<Method> minimalMethods =
3745 +            Stream.of(Object.class, CompletionStage.class)
3746 +            .flatMap((klazz) -> Stream.of(klazz.getMethods()))
3747 +            .filter(isNotStatic)
3748 +            .collect(Collectors.toList());
3749 +        // Methods from CompletableFuture permitted NOT to throw UOE
3750 +        String[] signatureWhitelist = {
3751 +            "newIncompleteFuture[]",
3752 +            "defaultExecutor[]",
3753 +            "minimalCompletionStage[]",
3754 +            "copy[]",
3755 +        };
3756 +        Set<String> permittedMethodSignatures =
3757 +            Stream.concat(minimalMethods.stream().map(toSignature),
3758 +                          Stream.of(signatureWhitelist))
3759 +            .collect(Collectors.toSet());
3760 +        List<Method> allMethods = Stream.of(CompletableFuture.class.getMethods())
3761 +            .filter(isNotStatic)
3762 +            .filter((method) -> !permittedMethodSignatures.contains(toSignature.apply(method)))
3763 +            .collect(Collectors.toList());
3764 +
3765 +        CompletionStage<Integer> minimalStage =
3766 +            new CompletableFuture<Integer>().minimalCompletionStage();
3767 +
3768 +        List<Method> bugs = new ArrayList<>();
3769 +        for (Method method : allMethods) {
3770 +            Class<?>[] parameterTypes = method.getParameterTypes();
3771 +            Object[] args = new Object[parameterTypes.length];
3772 +            // Manufacture boxed primitives for primitive params
3773 +            for (int i = 0; i < args.length; i++) {
3774 +                Class<?> type = parameterTypes[i];
3775 +                if (parameterTypes[i] == boolean.class)
3776 +                    args[i] = false;
3777 +                else if (parameterTypes[i] == int.class)
3778 +                    args[i] = 0;
3779 +                else if (parameterTypes[i] == long.class)
3780 +                    args[i] = 0L;
3781 +            }
3782 +            try {
3783 +                method.invoke(minimalStage, args);
3784 +                bugs.add(method);
3785 +            }
3786 +            catch (java.lang.reflect.InvocationTargetException expected) {
3787 +                if (! (expected.getCause() instanceof UnsupportedOperationException)) {
3788 +                    bugs.add(method);
3789 +                    // expected.getCause().printStackTrace();
3790 +                }
3791 +            }
3792 +            catch (ReflectiveOperationException bad) { throw new Error(bad); }
3793 +        }
3794 +        if (!bugs.isEmpty())
3795 +            throw new Error("Methods did not throw UOE: " + bugs.toString());
3796 +    }
3797 +
3798 +    static class Monad {
3799 +        static class ZeroException extends RuntimeException {
3800 +            public ZeroException() { super("monadic zero"); }
3801 +        }
3802 +        // "return", "unit"
3803 +        static <T> CompletableFuture<T> unit(T value) {
3804 +            return completedFuture(value);
3805 +        }
3806 +        // monadic zero ?
3807 +        static <T> CompletableFuture<T> zero() {
3808 +            return failedFuture(new ZeroException());
3809 +        }
3810 +        // >=>
3811 +        static <T,U,V> Function<T, CompletableFuture<V>> compose
3812 +            (Function<T, CompletableFuture<U>> f,
3813 +             Function<U, CompletableFuture<V>> g) {
3814 +            return (x) -> f.apply(x).thenCompose(g);
3815 +        }
3816 +
3817 +        static void assertZero(CompletableFuture<?> f) {
3818 +            try {
3819 +                f.getNow(null);
3820 +                throw new AssertionFailedError("should throw");
3821 +            } catch (CompletionException success) {
3822 +                assertTrue(success.getCause() instanceof ZeroException);
3823 +            }
3824 +        }
3825 +
3826 +        static <T> void assertFutureEquals(CompletableFuture<T> f,
3827 +                                           CompletableFuture<T> g) {
3828 +            T fval = null, gval = null;
3829 +            Throwable fex = null, gex = null;
3830 +
3831 +            try { fval = f.get(); }
3832 +            catch (ExecutionException ex) { fex = ex.getCause(); }
3833 +            catch (Throwable ex) { fex = ex; }
3834 +
3835 +            try { gval = g.get(); }
3836 +            catch (ExecutionException ex) { gex = ex.getCause(); }
3837 +            catch (Throwable ex) { gex = ex; }
3838 +
3839 +            if (fex != null || gex != null)
3840 +                assertSame(fex.getClass(), gex.getClass());
3841 +            else
3842 +                assertEquals(fval, gval);
3843 +        }
3844 +
3845 +        static class PlusFuture<T> extends CompletableFuture<T> {
3846 +            AtomicReference<Throwable> firstFailure = new AtomicReference<>(null);
3847 +        }
3848 +
3849 +        /** Implements "monadic plus". */
3850 +        static <T> CompletableFuture<T> plus(CompletableFuture<? extends T> f,
3851 +                                             CompletableFuture<? extends T> g) {
3852 +            PlusFuture<T> plus = new PlusFuture<T>();
3853 +            BiConsumer<T, Throwable> action = (T result, Throwable ex) -> {
3854 +                try {
3855 +                    if (ex == null) {
3856 +                        if (plus.complete(result))
3857 +                            if (plus.firstFailure.get() != null)
3858 +                                plus.firstFailure.set(null);
3859 +                    }
3860 +                    else if (plus.firstFailure.compareAndSet(null, ex)) {
3861 +                        if (plus.isDone())
3862 +                            plus.firstFailure.set(null);
3863 +                    }
3864 +                    else {
3865 +                        // first failure has precedence
3866 +                        Throwable first = plus.firstFailure.getAndSet(null);
3867 +
3868 +                        // may fail with "Self-suppression not permitted"
3869 +                        try { first.addSuppressed(ex); }
3870 +                        catch (Exception ignored) {}
3871 +
3872 +                        plus.completeExceptionally(first);
3873 +                    }
3874 +                } catch (Throwable unexpected) {
3875 +                    plus.completeExceptionally(unexpected);
3876 +                }
3877 +            };
3878 +            f.whenComplete(action);
3879 +            g.whenComplete(action);
3880 +            return plus;
3881 +        }
3882 +    }
3883 +
3884 +    /**
3885 +     * CompletableFuture is an additive monad - sort of.
3886 +     * https://en.wikipedia.org/wiki/Monad_(functional_programming)#Additive_monads
3887 +     */
3888 +    public void testAdditiveMonad() throws Throwable {
3889 +        Function<Long, CompletableFuture<Long>> unit = Monad::unit;
3890 +        CompletableFuture<Long> zero = Monad.zero();
3891 +
3892 +        // Some mutually non-commutative functions
3893 +        Function<Long, CompletableFuture<Long>> triple
3894 +            = (x) -> Monad.unit(3 * x);
3895 +        Function<Long, CompletableFuture<Long>> inc
3896 +            = (x) -> Monad.unit(x + 1);
3897 +
3898 +        // unit is a right identity: m >>= unit === m
3899 +        Monad.assertFutureEquals(inc.apply(5L).thenCompose(unit),
3900 +                                 inc.apply(5L));
3901 +        // unit is a left identity: (unit x) >>= f === f x
3902 +        Monad.assertFutureEquals(unit.apply(5L).thenCompose(inc),
3903 +                                 inc.apply(5L));
3904 +
3905 +        // associativity: (m >>= f) >>= g === m >>= ( \x -> (f x >>= g) )
3906 +        Monad.assertFutureEquals(
3907 +            unit.apply(5L).thenCompose(inc).thenCompose(triple),
3908 +            unit.apply(5L).thenCompose((x) -> inc.apply(x).thenCompose(triple)));
3909 +
3910 +        // The case for CompletableFuture as an additive monad is weaker...
3911 +
3912 +        // zero is a monadic zero
3913 +        Monad.assertZero(zero);
3914 +
3915 +        // left zero: zero >>= f === zero
3916 +        Monad.assertZero(zero.thenCompose(inc));
3917 +        // right zero: f >>= (\x -> zero) === zero
3918 +        Monad.assertZero(inc.apply(5L).thenCompose((x) -> zero));
3919 +
3920 +        // f plus zero === f
3921 +        Monad.assertFutureEquals(Monad.unit(5L),
3922 +                                 Monad.plus(Monad.unit(5L), zero));
3923 +        // zero plus f === f
3924 +        Monad.assertFutureEquals(Monad.unit(5L),
3925 +                                 Monad.plus(zero, Monad.unit(5L)));
3926 +        // zero plus zero === zero
3927 +        Monad.assertZero(Monad.plus(zero, zero));
3928 +        {
3929 +            CompletableFuture<Long> f = Monad.plus(Monad.unit(5L),
3930 +                                                   Monad.unit(8L));
3931 +            // non-determinism
3932 +            assertTrue(f.get() == 5L || f.get() == 8L);
3933 +        }
3934 +
3935 +        CompletableFuture<Long> godot = new CompletableFuture<>();
3936 +        // f plus godot === f (doesn't wait for godot)
3937 +        Monad.assertFutureEquals(Monad.unit(5L),
3938 +                                 Monad.plus(Monad.unit(5L), godot));
3939 +        // godot plus f === f (doesn't wait for godot)
3940 +        Monad.assertFutureEquals(Monad.unit(5L),
3941 +                                 Monad.plus(godot, Monad.unit(5L)));
3942 +    }
3943 +
3944 +    /**
3945 +     * A single CompletableFuture with many dependents.
3946 +     * A demo of scalability - runtime is O(n).
3947 +     */
3948 +    public void testManyDependents() throws Throwable {
3949 +        final int n = 1_000;
3950 +        final CompletableFuture<Void> head = new CompletableFuture<>();
3951 +        final CompletableFuture<Void> complete = CompletableFuture.completedFuture((Void)null);
3952 +        final AtomicInteger count = new AtomicInteger(0);
3953 +        for (int i = 0; i < n; i++) {
3954 +            head.thenRun(() -> count.getAndIncrement());
3955 +            head.thenAccept((x) -> count.getAndIncrement());
3956 +            head.thenApply((x) -> count.getAndIncrement());
3957 +
3958 +            head.runAfterBoth(complete, () -> count.getAndIncrement());
3959 +            head.thenAcceptBoth(complete, (x, y) -> count.getAndIncrement());
3960 +            head.thenCombine(complete, (x, y) -> count.getAndIncrement());
3961 +            complete.runAfterBoth(head, () -> count.getAndIncrement());
3962 +            complete.thenAcceptBoth(head, (x, y) -> count.getAndIncrement());
3963 +            complete.thenCombine(head, (x, y) -> count.getAndIncrement());
3964 +
3965 +            head.runAfterEither(new CompletableFuture<Void>(), () -> count.getAndIncrement());
3966 +            head.acceptEither(new CompletableFuture<Void>(), (x) -> count.getAndIncrement());
3967 +            head.applyToEither(new CompletableFuture<Void>(), (x) -> count.getAndIncrement());
3968 +            new CompletableFuture<Void>().runAfterEither(head, () -> count.getAndIncrement());
3969 +            new CompletableFuture<Void>().acceptEither(head, (x) -> count.getAndIncrement());
3970 +            new CompletableFuture<Void>().applyToEither(head, (x) -> count.getAndIncrement());
3971 +        }
3972 +        head.complete(null);
3973 +        assertEquals(5 * 3 * n, count.get());
3974 +    }
3975 +
3976 + //     static <U> U join(CompletionStage<U> stage) {
3977 + //         CompletableFuture<U> f = new CompletableFuture<>();
3978 + //         stage.whenComplete((v, ex) -> {
3979 + //             if (ex != null) f.completeExceptionally(ex); else f.complete(v);
3980 + //         });
3981 + //         return f.join();
3982 + //     }
3983 +
3984 + //     static <U> boolean isDone(CompletionStage<U> stage) {
3985 + //         CompletableFuture<U> f = new CompletableFuture<>();
3986 + //         stage.whenComplete((v, ex) -> {
3987 + //             if (ex != null) f.completeExceptionally(ex); else f.complete(v);
3988 + //         });
3989 + //         return f.isDone();
3990 + //     }
3991 +
3992 + //     static <U> U join2(CompletionStage<U> stage) {
3993 + //         return stage.toCompletableFuture().copy().join();
3994 + //     }
3995 +
3996 + //     static <U> boolean isDone2(CompletionStage<U> stage) {
3997 + //         return stage.toCompletableFuture().copy().isDone();
3998 + //     }
3999 +
4000   }

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