8210971: Add exception handling methods to CompletionStage and CompletableFuture

Reviewed-by: martin, chegar

src/java.base/share/classes/java/util/concurrent/CompletableFuture.java

@@ -957,17 +957,17 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
     @SuppressWarnings("serial")
     static final class UniExceptionally<T> extends UniCompletion<T,T> {
         Function<? super Throwable, ? extends T> fn;
-        UniExceptionally(CompletableFuture<T> dep, CompletableFuture<T> src,
+        UniExceptionally(Executor executor,
+                         CompletableFuture<T> dep, CompletableFuture<T> src,
                          Function<? super Throwable, ? extends T> fn) {
-            super(null, dep, src); this.fn = fn;
+            super(executor, dep, src); this.fn = fn;
         }
-        final CompletableFuture<T> tryFire(int mode) { // never ASYNC
+        final CompletableFuture<T> tryFire(int mode) {
-            // assert mode != ASYNC;
             CompletableFuture<T> d; CompletableFuture<T> a;
             Object r; Function<? super Throwable, ? extends T> f;
             if ((d = dep) == null || (f = fn) == null
                 || (a = src) == null || (r = a.result) == null
-                || !d.uniExceptionally(r, f, this))
+                || !d.uniExceptionally(r, f, mode > 0 ? null : this))
                 return null;
             dep = null; src = null; fn = null;
             return d.postFire(a, mode);
@@ -980,11 +980,11 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
         Throwable x;
         if (result == null) {
             try {
-                if (r instanceof AltResult && (x = ((AltResult)r).ex) != null) {
                 if (c != null && !c.claim())
                     return false;
+                if (r instanceof AltResult && (x = ((AltResult)r).ex) != null)
                     completeValue(f.apply(x));
-                } else
+                else
                     internalComplete(r);
             } catch (Throwable ex) {
                 completeThrowable(ex);
@@ -994,14 +994,88 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
     }
 
     private CompletableFuture<T> uniExceptionallyStage(
-        Function<Throwable, ? extends T> f) {
+        Executor e, Function<Throwable, ? extends T> f) {
         if (f == null) throw new NullPointerException();
         CompletableFuture<T> d = newIncompleteFuture();
         Object r;
         if ((r = result) == null)
-            unipush(new UniExceptionally<T>(d, this, f));
+            unipush(new UniExceptionally<T>(e, d, this, f));
-        else
+        else if (e == null)
             d.uniExceptionally(r, f, null);
+        else {
+            try {
+                e.execute(new UniExceptionally<T>(null, d, this, f));
+            } catch (Throwable ex) {
+                d.result = encodeThrowable(ex);
+            }
+        }
+        return d;
+    }
+
+    @SuppressWarnings("serial")
+    static final class UniComposeExceptionally<T> extends UniCompletion<T,T> {
+        Function<Throwable, ? extends CompletionStage<T>> fn;
+        UniComposeExceptionally(Executor executor, CompletableFuture<T> dep,
+                                CompletableFuture<T> src,
+                                Function<Throwable, ? extends CompletionStage<T>> fn) {
+            super(executor, dep, src); this.fn = fn;
+        }
+        final CompletableFuture<T> tryFire(int mode) {
+            CompletableFuture<T> d; CompletableFuture<T> a;
+            Function<Throwable, ? extends CompletionStage<T>> f;
+            Object r; Throwable x;
+            if ((d = dep) == null || (f = fn) == null
+                || (a = src) == null || (r = a.result) == null)
+                return null;
+            if (d.result == null) {
+                if ((r instanceof AltResult) &&
+                    (x = ((AltResult)r).ex) != null) {
+                    try {
+                        if (mode <= 0 && !claim())
+                            return null;
+                        CompletableFuture<T> g = f.apply(x).toCompletableFuture();
+                        if ((r = g.result) != null)
+                            d.completeRelay(r);
+                        else {
+                            g.unipush(new UniRelay<T,T>(d, g));
+                            if (d.result == null)
+                                return null;
+                        }
+                    } catch (Throwable ex) {
+                        d.completeThrowable(ex);
+                    }
+                }
+                else
+                    d.internalComplete(r);
+            }
+            dep = null; src = null; fn = null;
+            return d.postFire(a, mode);
+        }
+    }
+
+    private CompletableFuture<T> uniComposeExceptionallyStage(
+        Executor e, Function<Throwable, ? extends CompletionStage<T>> f) {
+        if (f == null) throw new NullPointerException();
+        CompletableFuture<T> d = newIncompleteFuture();
+        Object r, s; Throwable x;
+        if ((r = result) == null)
+            unipush(new UniComposeExceptionally<T>(e, d, this, f));
+        else if (!(r instanceof AltResult) || (x = ((AltResult)r).ex) == null)
+            d.internalComplete(r);
+        else
+            try {
+                if (e != null)
+                    e.execute(new UniComposeExceptionally<T>(null, d, this, f));
+                else {
+                    CompletableFuture<T> g = f.apply(x).toCompletableFuture();
+                    if ((s = g.result) != null)
+                        d.result = encodeRelay(s);
+                    else
+                        g.unipush(new UniRelay<T,T>(d, g));
+                }
+            } catch (Throwable ex) {
+                d.result = encodeThrowable(ex);
+            }
         return d;
     }
 
@@ -1093,7 +1167,7 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
         Object r, s; Throwable x;
         if ((r = result) == null)
             unipush(new UniCompose<T,V>(e, d, this, f));
-        else if (e == null) {
+        else {
             if (r instanceof AltResult) {
                 if ((x = ((AltResult)r).ex) != null) {
                     d.result = encodeThrowable(x, r);
@@ -1102,23 +1176,20 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
                 r = null;
             }
             try {
+                if (e != null)
+                    e.execute(new UniCompose<T,V>(null, d, this, f));
+                else {
                     @SuppressWarnings("unchecked") T t = (T) r;
                     CompletableFuture<V> g = f.apply(t).toCompletableFuture();
                     if ((s = g.result) != null)
                         d.result = encodeRelay(s);
-                else {
+                    else
                         g.unipush(new UniRelay<V,V>(d, g));
                 }
             } catch (Throwable ex) {
                 d.result = encodeThrowable(ex);
             }
         }
-        else
-            try {
-                e.execute(new UniCompose<T,V>(null, d, this, f));
-            } catch (Throwable ex) {
-                d.result = encodeThrowable(ex);
-            }
         return d;
     }
 
@@ -1898,7 +1969,7 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
      * Creates a new complete CompletableFuture with given encoded result.
      */
     CompletableFuture(Object r) {
-        this.result = r;
+        RESULT.setRelease(this, r);
     }
 
     /**
@@ -2285,28 +2356,36 @@ public class CompletableFuture<T> implements Future<T>, CompletionStage<T> {
         return this;
     }
 
-    // not in interface CompletionStage
-
-    /**
-     * Returns a new CompletableFuture that is completed when this
-     * CompletableFuture completes, with the result of the given
-     * function of the exception triggering this CompletableFuture's
-     * completion when it completes exceptionally; otherwise, if this
-     * CompletableFuture completes normally, then the returned
-     * CompletableFuture also completes normally with the same value.
-     * Note: More flexible versions of this functionality are
-     * available using methods {@code whenComplete} and {@code handle}.
-     *
-     * @param fn the function to use to compute the value of the
-     * returned CompletableFuture if this CompletableFuture completed
-     * exceptionally
-     * @return the new CompletableFuture
-     */
     public CompletableFuture<T> exceptionally(
         Function<Throwable, ? extends T> fn) {
-        return uniExceptionallyStage(fn);
+        return uniExceptionallyStage(null, fn);
     }
 
+    public CompletableFuture<T> exceptionallyAsync(
+        Function<Throwable, ? extends T> fn) {
+        return uniExceptionallyStage(defaultExecutor(), fn);
+    }
+
+    public CompletableFuture<T> exceptionallyAsync(
+        Function<Throwable, ? extends T> fn, Executor executor) {
+        return uniExceptionallyStage(screenExecutor(executor), fn);
+    }
+
+    public CompletableFuture<T> exceptionallyCompose(
+        Function<Throwable, ? extends CompletionStage<T>> fn) {
+        return uniComposeExceptionallyStage(null, fn);
+    }
+
+    public CompletableFuture<T> exceptionallyComposeAsync(
+        Function<Throwable, ? extends CompletionStage<T>> fn) {
+        return uniComposeExceptionallyStage(defaultExecutor(), fn);
+    }
+
+    public CompletableFuture<T> exceptionallyComposeAsync(
+        Function<Throwable, ? extends CompletionStage<T>> fn,
+        Executor executor) {
+        return uniComposeExceptionallyStage(screenExecutor(executor), fn);
+    }
 
     /* ------------- Arbitrary-arity constructions -------------- */
 

src/java.base/share/classes/java/util/concurrent/CompletionStage.java

@@ -850,6 +850,130 @@ public interface CompletionStage<T> {
     public CompletionStage<T> exceptionally
         (Function<Throwable, ? extends T> fn);
 
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * exceptionally, is executed with this stage's exception as the
+     * argument to the supplied function, using this stage's default
+     * asynchronous execution facility.  Otherwise, if this stage
+     * completes normally, then the returned stage also completes
+     * normally with the same value.
+     *
+     * @implSpec The default implementation invokes {@link #handle},
+     * relaying to {@link #handleAsync} on exception, then {@link
+     * #thenCompose} for result.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage if this CompletionStage completed
+     * exceptionally
+     * @return the new CompletionStage
+     * @since 12
+     */
+    public default CompletionStage<T> exceptionallyAsync
+        (Function<Throwable, ? extends T> fn) {
+        return handle((r, ex) -> (ex == null)
+                      ? this
+                      : this.<T>handleAsync((r1, ex1) -> fn.apply(ex1)))
+            .thenCompose(Function.identity());
+    }
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * exceptionally, is executed with this stage's exception as the
+     * argument to the supplied function, using the supplied Executor.
+     * Otherwise, if this stage completes normally, then the returned
+     * stage also completes normally with the same value.
+     *
+     * @implSpec The default implementation invokes {@link #handle},
+     * relaying to {@link #handleAsync} on exception, then {@link
+     * #thenCompose} for result.
+     *
+     * @param fn the function to use to compute the value of the
+     * returned CompletionStage if this CompletionStage completed
+     * exceptionally
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     * @since 12
+     */
+    public default CompletionStage<T> exceptionallyAsync
+        (Function<Throwable, ? extends T> fn, Executor executor) {
+        return handle((r, ex) -> (ex == null)
+                      ? this
+                      : this.<T>handleAsync((r1, ex1) -> fn.apply(ex1), executor))
+            .thenCompose(Function.identity());
+    }
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * exceptionally, is composed using the results of the supplied
+     * function applied to this stage's exception.
+     *
+     * @implSpec The default implementation invokes {@link #handle},
+     * invoking the given function on exception, then {@link
+     * #thenCompose} for result.
+     *
+     * @param fn the function to use to compute the returned
+     * CompletionStage if this CompletionStage completed exceptionally
+     * @return the new CompletionStage
+     * @since 12
+     */
+    public default CompletionStage<T> exceptionallyCompose
+        (Function<Throwable, ? extends CompletionStage<T>> fn) {
+        return handle((r, ex) -> (ex == null)
+                      ? this
+                      : fn.apply(ex))
+            .thenCompose(Function.identity());
+    }
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * exceptionally, is composed using the results of the supplied
+     * function applied to this stage's exception, using this stage's
+     * default asynchronous execution facility.
+     *
+     * @implSpec The default implementation invokes {@link #handle},
+     * relaying to {@link #handleAsync} on exception, then {@link
+     * #thenCompose} for result.
+     *
+     * @param fn the function to use to compute the returned
+     * CompletionStage if this CompletionStage completed exceptionally
+     * @return the new CompletionStage
+     * @since 12
+     */
+    public default CompletionStage<T> exceptionallyComposeAsync
+        (Function<Throwable, ? extends CompletionStage<T>> fn) {
+        return handle((r, ex) -> (ex == null)
+                      ? this
+                      : this.handleAsync((r1, ex1) -> fn.apply(ex1))
+                        .thenCompose(Function.identity()))
+            .thenCompose(Function.identity());
+    }
+
+    /**
+     * Returns a new CompletionStage that, when this stage completes
+     * exceptionally, is composed using the results of the supplied
+     * function applied to this stage's exception, using the
+     * supplied Executor.
+     *
+     * @implSpec The default implementation invokes {@link #handle},
+     * relaying to {@link #handleAsync} on exception, then {@link
+     * #thenCompose} for result.
+     *
+     * @param fn the function to use to compute the returned
+     * CompletionStage if this CompletionStage completed exceptionally
+     * @param executor the executor to use for asynchronous execution
+     * @return the new CompletionStage
+     * @since 12
+     */
+    public default CompletionStage<T> exceptionallyComposeAsync
+        (Function<Throwable, ? extends CompletionStage<T>> fn,
+         Executor executor) {
+        return handle((r, ex) -> (ex == null)
+                      ? this
+                      : this.handleAsync((r1, ex1) -> fn.apply(ex1), executor)
+                        .thenCompose(Function.identity()))
+            .thenCompose(Function.identity());
+    }
+
     /**
      * Returns a {@link CompletableFuture} maintaining the same
      * completion properties as this stage. If this stage is already a

test/jdk/java/util/concurrent/tck/CompletableFutureTest.java

@@ -86,9 +86,13 @@ public class CompletableFutureTest extends JSR166TestCase {
         assertFalse(f.isDone());
         assertFalse(f.isCancelled());
         assertTrue(f.toString().matches(".*\\[.*Not completed.*\\]"));
+
+        Object result = null;
         try {
-            assertNull(f.getNow(null));
+            result = f.getNow(null);
         } catch (Throwable fail) { threadUnexpectedException(fail); }
+        assertNull(result);
+
         try {
             f.get(randomExpiredTimeout(), randomTimeUnit());
             shouldThrow();
@@ -97,14 +101,18 @@ public class CompletableFutureTest extends JSR166TestCase {
         catch (Throwable fail) { threadUnexpectedException(fail); }
     }
 
-    <T> void checkCompletedNormally(CompletableFuture<T> f, T value) {
+    <T> void checkCompletedNormally(CompletableFuture<T> f, T expectedValue) {
-        checkTimedGet(f, value);
+        checkTimedGet(f, expectedValue);
 
+        assertEquals(expectedValue, f.join());
+        assertEquals(expectedValue, f.getNow(null));
+
+        T result = null;
         try {
-            assertEquals(value, f.join());
+            result = f.get();
-            assertEquals(value, f.getNow(null));
-            assertEquals(value, f.get());
         } catch (Throwable fail) { threadUnexpectedException(fail); }
+        assertEquals(expectedValue, result);
+
         assertTrue(f.isDone());
         assertFalse(f.isCancelled());
         assertFalse(f.isCompletedExceptionally());
@@ -570,9 +578,28 @@ public class CompletableFutureTest extends JSR166TestCase {
         public CompletableFuture<Integer> apply(Integer x) {
             invoked();
             value = x;
-            CompletableFuture<Integer> f = new CompletableFuture<>();
+            return CompletableFuture.completedFuture(inc(x));
-            assertTrue(f.complete(inc(x)));
+        }
-            return f;
+    }
+
+    static class FailingExceptionalCompletableFutureFunction extends CheckedAction
+        implements Function<Throwable, CompletableFuture<Integer>>
+    {
+        final CFException ex;
+        FailingExceptionalCompletableFutureFunction(ExecutionMode m) { super(m); ex = new CFException(); }
+        public CompletableFuture<Integer> apply(Throwable x) {
+            invoked();
+            throw ex;
+        }
+    }
+
+    static class ExceptionalCompletableFutureFunction extends CheckedAction
+        implements Function<Throwable, CompletionStage<Integer>> {
+        final Integer value = 3;
+        ExceptionalCompletableFutureFunction(ExecutionMode m) { super(m); }
+        public CompletionStage<Integer> apply(Throwable x) {
+            invoked();
+            return CompletableFuture.completedFuture(value);
         }
     }
 
@@ -691,8 +718,16 @@ public class CompletableFutureTest extends JSR166TestCase {
                  Function<? super T,U> a) {
                 return f.applyToEither(g, a);
             }
+            public <T> CompletableFuture<T> exceptionally
+                (CompletableFuture<T> f,
+                 Function<Throwable, ? extends T> fn) {
+                return f.exceptionally(fn);
+            }
+            public <T> CompletableFuture<T> exceptionallyCompose
+                (CompletableFuture<T> f, Function<Throwable, ? extends CompletionStage<T>> fn) {
+                return f.exceptionallyCompose(fn);
+            }
         },
-
         ASYNC {
             public void checkExecutionMode() {
                 assertEquals(defaultExecutorIsCommonPool,
@@ -765,6 +800,17 @@ public class CompletableFutureTest extends JSR166TestCase {
                  Function<? super T,U> a) {
                 return f.applyToEitherAsync(g, a);
             }
+            public <T> CompletableFuture<T> exceptionally
+                (CompletableFuture<T> f,
+                 Function<Throwable, ? extends T> fn) {
+                return f.exceptionallyAsync(fn);
+            }
+
+            public <T> CompletableFuture<T> exceptionallyCompose
+                (CompletableFuture<T> f, Function<Throwable, ? extends CompletionStage<T>> fn) {
+                return f.exceptionallyComposeAsync(fn);
+            }
+
         },
 
         EXECUTOR {
@@ -838,6 +884,16 @@ public class CompletableFutureTest extends JSR166TestCase {
                  Function<? super T,U> a) {
                 return f.applyToEitherAsync(g, a, new ThreadExecutor());
             }
+            public <T> CompletableFuture<T> exceptionally
+                (CompletableFuture<T> f,
+                 Function<Throwable, ? extends T> fn) {
+                return f.exceptionallyAsync(fn, new ThreadExecutor());
+            }
+            public <T> CompletableFuture<T> exceptionallyCompose
+                (CompletableFuture<T> f, Function<Throwable, ? extends CompletionStage<T>> fn) {
+                return f.exceptionallyComposeAsync(fn, new ThreadExecutor());
+            }
+
         };
 
         public abstract void checkExecutionMode();
@@ -880,6 +936,12 @@ public class CompletableFutureTest extends JSR166TestCase {
             (CompletableFuture<T> f,
              CompletionStage<? extends T> g,
              Function<? super T,U> a);
+        public abstract <T> CompletableFuture<T> exceptionally
+            (CompletableFuture<T> f,
+             Function<Throwable, ? extends T> fn);
+        public abstract <T> CompletableFuture<T> exceptionallyCompose
+            (CompletableFuture<T> f,
+             Function<Throwable, ? extends CompletionStage<T>> fn);
     }
 
     /**
@@ -887,15 +949,14 @@ public class CompletableFutureTest extends JSR166TestCase {
      * normally, and source result is propagated
      */
     public void testExceptionally_normalCompletion() {
+        for (ExecutionMode m : ExecutionMode.values())
         for (boolean createIncomplete : new boolean[] { true, false })
         for (Integer v1 : new Integer[] { 1, null })
     {
-        final AtomicInteger a = new AtomicInteger(0);
         final CompletableFuture<Integer> f = new CompletableFuture<>();
         if (!createIncomplete) assertTrue(f.complete(v1));
-        final CompletableFuture<Integer> g = f.exceptionally
+        final CompletableFuture<Integer> g = m.exceptionally
-            ((Throwable t) -> {
+            (f, (Throwable t) -> {
-                a.getAndIncrement();
                 threadFail("should not be called");
                 return null;            // unreached
             });
@@ -903,7 +964,6 @@ public class CompletableFutureTest extends JSR166TestCase {
 
         checkCompletedNormally(g, v1);
         checkCompletedNormally(f, v1);
-        assertEquals(0, a.get());
     }}
 
     /**
@@ -911,6 +971,7 @@ public class CompletableFutureTest extends JSR166TestCase {
      * exception
      */
     public void testExceptionally_exceptionalCompletion() {
+        for (ExecutionMode m : ExecutionMode.values())
         for (boolean createIncomplete : new boolean[] { true, false })
         for (Integer v1 : new Integer[] { 1, null })
     {
@@ -918,9 +979,9 @@ public class CompletableFutureTest extends JSR166TestCase {
         final CFException ex = new CFException();
         final CompletableFuture<Integer> f = new CompletableFuture<>();
         if (!createIncomplete) f.completeExceptionally(ex);
-        final CompletableFuture<Integer> g = f.exceptionally
+        final CompletableFuture<Integer> g = m.exceptionally
-            ((Throwable t) -> {
+            (f, (Throwable t) -> {
-                ExecutionMode.SYNC.checkExecutionMode();
+                m.checkExecutionMode();
                 threadAssertSame(t, ex);
                 a.getAndIncrement();
                 return v1;
@@ -936,6 +997,7 @@ public class CompletableFutureTest extends JSR166TestCase {
      * exceptionally with that exception
      */
     public void testExceptionally_exceptionalCompletionActionFailed() {
+        for (ExecutionMode m : ExecutionMode.values())
         for (boolean createIncomplete : new boolean[] { true, false })
     {
         final AtomicInteger a = new AtomicInteger(0);
@@ -943,9 +1005,9 @@ public class CompletableFutureTest extends JSR166TestCase {
         final CFException ex2 = new CFException();
         final CompletableFuture<Integer> f = new CompletableFuture<>();
         if (!createIncomplete) f.completeExceptionally(ex1);
-        final CompletableFuture<Integer> g = f.exceptionally
+        final CompletableFuture<Integer> g = m.exceptionally
-            ((Throwable t) -> {
+            (f, (Throwable t) -> {
-                ExecutionMode.SYNC.checkExecutionMode();
+                m.checkExecutionMode();
                 threadAssertSame(t, ex1);
                 a.getAndIncrement();
                 throw ex2;
@@ -3116,6 +3178,121 @@ public class CompletableFutureTest extends JSR166TestCase {
         checkCompletedNormally(f, v1);
     }}
 
+    /**
+     * exceptionallyCompose result completes normally after normal
+     * completion of source
+     */
+    public void testExceptionallyCompose_normalCompletion() {
+        for (ExecutionMode m : ExecutionMode.values())
+        for (boolean createIncomplete : new boolean[] { true, false })
+        for (Integer v1 : new Integer[] { 1, null })
+    {
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(m);
+        if (!createIncomplete) assertTrue(f.complete(v1));
+        final CompletableFuture<Integer> g = m.exceptionallyCompose(f, r);
+        if (createIncomplete) assertTrue(f.complete(v1));
+
+        checkCompletedNormally(f, v1);
+        checkCompletedNormally(g, v1);
+        r.assertNotInvoked();
+    }}
+
+    /**
+     * exceptionallyCompose result completes normally after exceptional
+     * completion of source
+     */
+    public void testExceptionallyCompose_exceptionalCompletion() {
+        for (ExecutionMode m : ExecutionMode.values())
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(m);
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletableFuture<Integer> g = m.exceptionallyCompose(f, r);
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedNormally(g, r.value);
+        r.assertInvoked();
+    }}
+
+    /**
+     * exceptionallyCompose completes exceptionally on exception if action does
+     */
+    public void testExceptionallyCompose_actionFailed() {
+        for (ExecutionMode m : ExecutionMode.values())
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final FailingExceptionalCompletableFutureFunction r
+            = new FailingExceptionalCompletableFutureFunction(m);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletableFuture<Integer> g = m.exceptionallyCompose(f, r);
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedWithWrappedException(g, r.ex);
+        r.assertInvoked();
+    }}
+
+    /**
+     * exceptionallyCompose result completes exceptionally if the
+     * result of the action does
+     */
+    public void testExceptionallyCompose_actionReturnsFailingFuture() {
+        for (ExecutionMode m : ExecutionMode.values())
+        for (int order = 0; order < 6; order++)
+    {
+        final CFException ex0 = new CFException();
+        final CFException ex = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final CompletableFuture<Integer> g = new CompletableFuture<>();
+        final CompletableFuture<Integer> h;
+        // Test all permutations of orders
+        switch (order) {
+        case 0:
+            assertTrue(f.completeExceptionally(ex0));
+            assertTrue(g.completeExceptionally(ex));
+            h = m.exceptionallyCompose(f, (x -> g));
+            break;
+        case 1:
+            assertTrue(f.completeExceptionally(ex0));
+            h = m.exceptionallyCompose(f, (x -> g));
+            assertTrue(g.completeExceptionally(ex));
+            break;
+        case 2:
+            assertTrue(g.completeExceptionally(ex));
+            assertTrue(f.completeExceptionally(ex0));
+            h = m.exceptionallyCompose(f, (x -> g));
+            break;
+        case 3:
+            assertTrue(g.completeExceptionally(ex));
+            h = m.exceptionallyCompose(f, (x -> g));
+            assertTrue(f.completeExceptionally(ex0));
+            break;
+        case 4:
+            h = m.exceptionallyCompose(f, (x -> g));
+            assertTrue(f.completeExceptionally(ex0));
+            assertTrue(g.completeExceptionally(ex));
+            break;
+        case 5:
+            h = m.exceptionallyCompose(f, (x -> g));
+            assertTrue(f.completeExceptionally(ex0));
+            assertTrue(g.completeExceptionally(ex));
+            break;
+        default: throw new AssertionError();
+        }
+
+        checkCompletedExceptionally(g, ex);
+        checkCompletedWithWrappedException(h, ex);
+        checkCompletedExceptionally(f, ex0);
+    }}
+
     // other static methods
 
     /**
@@ -4527,4 +4704,429 @@ public class CompletableFutureTest extends JSR166TestCase {
 //         return stage.toCompletableFuture().copy().isDone();
 //     }
 
+    // For testing default implementations
+    // Only non-default interface methods defined.
+    static final class DelegatedCompletionStage<T> implements CompletionStage<T> {
+        final CompletableFuture<T> cf;
+        DelegatedCompletionStage(CompletableFuture<T> cf) { this.cf = cf; }
+        public CompletableFuture<T> toCompletableFuture() {
+            return cf; }
+        public CompletionStage<Void> thenRun
+            (Runnable action) {
+            return cf.thenRun(action); }
+        public CompletionStage<Void> thenRunAsync
+            (Runnable action) {
+            return cf.thenRunAsync(action); }
+        public CompletionStage<Void> thenRunAsync
+            (Runnable action,
+             Executor executor) {
+            return cf.thenRunAsync(action, executor); }
+        public CompletionStage<Void> thenAccept
+            (Consumer<? super T> action) {
+            return cf.thenAccept(action); }
+        public CompletionStage<Void> thenAcceptAsync
+            (Consumer<? super T> action) {
+            return cf.thenAcceptAsync(action); }
+        public CompletionStage<Void> thenAcceptAsync
+            (Consumer<? super T> action,
+             Executor executor) {
+            return cf.thenAcceptAsync(action, executor); }
+        public <U> CompletionStage<U> thenApply
+            (Function<? super T,? extends U> a) {
+            return cf.thenApply(a); }
+        public <U> CompletionStage<U> thenApplyAsync
+            (Function<? super T,? extends U> fn) {
+            return cf.thenApplyAsync(fn); }
+        public <U> CompletionStage<U> thenApplyAsync
+            (Function<? super T,? extends U> fn,
+             Executor executor) {
+            return cf.thenApplyAsync(fn, executor); }
+        public <U,V> CompletionStage<V> thenCombine
+            (CompletionStage<? extends U> other,
+             BiFunction<? super T,? super U,? extends V> fn) {
+            return cf.thenCombine(other, fn); }
+        public <U,V> CompletionStage<V> thenCombineAsync
+            (CompletionStage<? extends U> other,
+             BiFunction<? super T,? super U,? extends V> fn) {
+            return cf.thenCombineAsync(other, fn); }
+        public <U,V> CompletionStage<V> thenCombineAsync
+            (CompletionStage<? extends U> other,
+             BiFunction<? super T,? super U,? extends V> fn,
+             Executor executor) {
+            return cf.thenCombineAsync(other, fn, executor); }
+        public <U> CompletionStage<Void> thenAcceptBoth
+            (CompletionStage<? extends U> other,
+             BiConsumer<? super T, ? super U> action) {
+            return cf.thenAcceptBoth(other, action); }
+        public <U> CompletionStage<Void> thenAcceptBothAsync
+            (CompletionStage<? extends U> other,
+             BiConsumer<? super T, ? super U> action) {
+            return cf.thenAcceptBothAsync(other, action); }
+        public <U> CompletionStage<Void> thenAcceptBothAsync
+            (CompletionStage<? extends U> other,
+             BiConsumer<? super T, ? super U> action,
+             Executor executor) {
+            return cf.thenAcceptBothAsync(other, action, executor); }
+        public CompletionStage<Void> runAfterBoth
+            (CompletionStage<?> other,
+             Runnable action) {
+            return cf.runAfterBoth(other, action); }
+        public CompletionStage<Void> runAfterBothAsync
+            (CompletionStage<?> other,
+             Runnable action) {
+            return cf.runAfterBothAsync(other, action); }
+        public CompletionStage<Void> runAfterBothAsync
+            (CompletionStage<?> other,
+             Runnable action,
+             Executor executor) {
+            return cf.runAfterBothAsync(other, action, executor); }
+        public <U> CompletionStage<U> applyToEither
+            (CompletionStage<? extends T> other,
+             Function<? super T, U> fn) {
+            return cf.applyToEither(other, fn); }
+        public <U> CompletionStage<U> applyToEitherAsync
+            (CompletionStage<? extends T> other,
+             Function<? super T, U> fn) {
+            return cf.applyToEitherAsync(other, fn); }
+        public <U> CompletionStage<U> applyToEitherAsync
+            (CompletionStage<? extends T> other,
+             Function<? super T, U> fn,
+             Executor executor) {
+            return cf.applyToEitherAsync(other, fn, executor); }
+        public CompletionStage<Void> acceptEither
+            (CompletionStage<? extends T> other,
+             Consumer<? super T> action) {
+            return cf.acceptEither(other, action); }
+        public CompletionStage<Void> acceptEitherAsync
+            (CompletionStage<? extends T> other,
+             Consumer<? super T> action) {
+            return cf.acceptEitherAsync(other, action); }
+        public CompletionStage<Void> acceptEitherAsync
+            (CompletionStage<? extends T> other,
+             Consumer<? super T> action,
+             Executor executor) {
+            return cf.acceptEitherAsync(other, action, executor); }
+        public CompletionStage<Void> runAfterEither
+            (CompletionStage<?> other,
+             Runnable action) {
+            return cf.runAfterEither(other, action); }
+        public CompletionStage<Void> runAfterEitherAsync
+            (CompletionStage<?> other,
+             Runnable action) {
+            return cf.runAfterEitherAsync(other, action); }
+        public CompletionStage<Void> runAfterEitherAsync
+            (CompletionStage<?> other,
+             Runnable action,
+             Executor executor) {
+            return cf.runAfterEitherAsync(other, action, executor); }
+        public <U> CompletionStage<U> thenCompose
+            (Function<? super T, ? extends CompletionStage<U>> fn) {
+            return cf.thenCompose(fn); }
+        public <U> CompletionStage<U> thenComposeAsync
+            (Function<? super T, ? extends CompletionStage<U>> fn) {
+            return cf.thenComposeAsync(fn); }
+        public <U> CompletionStage<U> thenComposeAsync
+            (Function<? super T, ? extends CompletionStage<U>> fn,
+             Executor executor) {
+            return cf.thenComposeAsync(fn, executor); }
+        public <U> CompletionStage<U> handle
+            (BiFunction<? super T, Throwable, ? extends U> fn) {
+            return cf.handle(fn); }
+        public <U> CompletionStage<U> handleAsync
+            (BiFunction<? super T, Throwable, ? extends U> fn) {
+            return cf.handleAsync(fn); }
+        public <U> CompletionStage<U> handleAsync
+            (BiFunction<? super T, Throwable, ? extends U> fn,
+             Executor executor) {
+            return cf.handleAsync(fn, executor); }
+        public CompletionStage<T> whenComplete
+            (BiConsumer<? super T, ? super Throwable> action) {
+            return cf.whenComplete(action); }
+        public CompletionStage<T> whenCompleteAsync
+            (BiConsumer<? super T, ? super Throwable> action) {
+            return cf.whenCompleteAsync(action); }
+        public CompletionStage<T> whenCompleteAsync
+            (BiConsumer<? super T, ? super Throwable> action,
+             Executor executor) {
+            return cf.whenCompleteAsync(action, executor); }
+        public CompletionStage<T> exceptionally
+            (Function<Throwable, ? extends T> fn) {
+            return cf.exceptionally(fn); }
+    }
+
+    /**
+     * default-implemented exceptionallyAsync action is not invoked when
+     * source completes normally, and source result is propagated
+     */
+    public void testDefaultExceptionallyAsync_normalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+        for (Integer v1 : new Integer[] { 1, null })
+    {
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) assertTrue(f.complete(v1));
+        final CompletionStage<Integer> g = d.exceptionallyAsync
+            ((Throwable t) -> {
+                threadFail("should not be called");
+                return null;            // unreached
+            });
+        if (createIncomplete) assertTrue(f.complete(v1));
+
+        checkCompletedNormally(g.toCompletableFuture(), v1);
+    }}
+
+    /**
+     * default-implemented exceptionallyAsync action completes with
+     * function value on source exception
+     */
+    public void testDefaultExceptionallyAsync_exceptionalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+        for (Integer v1 : new Integer[] { 1, null })
+    {
+        final AtomicInteger a = new AtomicInteger(0);
+        final CFException ex = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyAsync
+            ((Throwable t) -> {
+                threadAssertSame(t, ex);
+                a.getAndIncrement();
+                return v1;
+            });
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedNormally(g.toCompletableFuture(), v1);
+        assertEquals(1, a.get());
+    }}
+
+    /**
+     * Under default implementation, if an "exceptionally action"
+     * throws an exception, it completes exceptionally with that
+     * exception
+     */
+    public void testDefaultExceptionallyAsync_exceptionalCompletionActionFailed() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final AtomicInteger a = new AtomicInteger(0);
+        final CFException ex1 = new CFException();
+        final CFException ex2 = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex1);
+        final CompletionStage<Integer> g = d.exceptionallyAsync
+            ((Throwable t) -> {
+                threadAssertSame(t, ex1);
+                a.getAndIncrement();
+                throw ex2;
+            });
+        if (createIncomplete) f.completeExceptionally(ex1);
+
+        checkCompletedWithWrappedException(g.toCompletableFuture(), ex2);
+        checkCompletedExceptionally(f, ex1);
+        checkCompletedExceptionally(d.toCompletableFuture(), ex1);
+        assertEquals(1, a.get());
+    }}
+
+    /**
+     * default-implemented exceptionallyCompose result completes
+     * normally after normal completion of source
+     */
+    public void testDefaultExceptionallyCompose_normalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+        for (Integer v1 : new Integer[] { 1, null })
+    {
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(ExecutionMode.SYNC);
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) assertTrue(f.complete(v1));
+        final CompletionStage<Integer> g = d.exceptionallyCompose(r);
+        if (createIncomplete) assertTrue(f.complete(v1));
+
+        checkCompletedNormally(f, v1);
+        checkCompletedNormally(g.toCompletableFuture(), v1);
+        r.assertNotInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyCompose result completes
+     * normally after exceptional completion of source
+     */
+    public void testDefaultExceptionallyCompose_exceptionalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(ExecutionMode.SYNC);
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyCompose(r);
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedNormally(g.toCompletableFuture(), r.value);
+        r.assertInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyCompose completes
+     * exceptionally on exception if action does
+     */
+    public void testDefaultExceptionallyCompose_actionFailed() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final FailingExceptionalCompletableFutureFunction r
+            = new FailingExceptionalCompletableFutureFunction(ExecutionMode.SYNC);
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyCompose(r);
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedWithWrappedException(g.toCompletableFuture(), r.ex);
+        r.assertInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyComposeAsync result completes
+     * normally after normal completion of source
+     */
+    public void testDefaultExceptionallyComposeAsync_normalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+        for (Integer v1 : new Integer[] { 1, null })
+    {
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(ExecutionMode.ASYNC);
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) assertTrue(f.complete(v1));
+        final CompletionStage<Integer> g = d.exceptionallyComposeAsync(r);
+        if (createIncomplete) assertTrue(f.complete(v1));
+
+        checkCompletedNormally(f, v1);
+        checkCompletedNormally(g.toCompletableFuture(), v1);
+        r.assertNotInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyComposeAsync result completes
+     * normally after exceptional completion of source
+     */
+    public void testDefaultExceptionallyComposeAsync_exceptionalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(ExecutionMode.ASYNC);
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyComposeAsync(r);
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedNormally(g.toCompletableFuture(), r.value);
+        r.assertInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyComposeAsync completes
+     * exceptionally on exception if action does
+     */
+    public void testDefaultExceptionallyComposeAsync_actionFailed() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final FailingExceptionalCompletableFutureFunction r
+            = new FailingExceptionalCompletableFutureFunction(ExecutionMode.ASYNC);
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyComposeAsync(r);
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedWithWrappedException(g.toCompletableFuture(), r.ex);
+        r.assertInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyComposeAsync result completes
+     * normally after normal completion of source
+     */
+    public void testDefaultExceptionallyComposeAsyncExecutor_normalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+        for (Integer v1 : new Integer[] { 1, null })
+    {
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(ExecutionMode.EXECUTOR);
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) assertTrue(f.complete(v1));
+        final CompletionStage<Integer> g = d.exceptionallyComposeAsync(r, new ThreadExecutor());
+        if (createIncomplete) assertTrue(f.complete(v1));
+
+        checkCompletedNormally(f, v1);
+        checkCompletedNormally(g.toCompletableFuture(), v1);
+        r.assertNotInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyComposeAsync result completes
+     * normally after exceptional completion of source
+     */
+    public void testDefaultExceptionallyComposeAsyncExecutor_exceptionalCompletion() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final ExceptionalCompletableFutureFunction r =
+            new ExceptionalCompletableFutureFunction(ExecutionMode.EXECUTOR);
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyComposeAsync(r, new ThreadExecutor());
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedNormally(g.toCompletableFuture(), r.value);
+        r.assertInvoked();
+    }}
+
+    /**
+     * default-implemented exceptionallyComposeAsync completes
+     * exceptionally on exception if action does
+     */
+    public void testDefaultExceptionallyComposeAsyncExecutor_actionFailed() {
+        for (boolean createIncomplete : new boolean[] { true, false })
+    {
+        final CFException ex = new CFException();
+        final CompletableFuture<Integer> f = new CompletableFuture<>();
+        final FailingExceptionalCompletableFutureFunction r
+            = new FailingExceptionalCompletableFutureFunction(ExecutionMode.EXECUTOR);
+        final DelegatedCompletionStage<Integer> d =
+            new DelegatedCompletionStage<Integer>(f);
+        if (!createIncomplete) f.completeExceptionally(ex);
+        final CompletionStage<Integer> g = d.exceptionallyComposeAsync(r, new ThreadExecutor());
+        if (createIncomplete) f.completeExceptionally(ex);
+
+        checkCompletedExceptionally(f, ex);
+        checkCompletedWithWrappedException(g.toCompletableFuture(), r.ex);
+        r.assertInvoked();
+    }}
+
 }