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import static java.util.concurrent.TimeUnit.MILLISECONDS; |
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import static java.util.concurrent.TimeUnit.SECONDS; |
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import static java.util.concurrent.CompletableFuture.completedFuture; |
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import static java.util.concurrent.CompletableFuture.failedFuture; |
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import java.lang.reflect.Method; |
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import java.lang.reflect.Modifier; |
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import java.util.function.BiFunction; |
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import java.util.function.Consumer; |
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import java.util.function.Function; |
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import java.util.function.Predicate; |
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import java.util.function.Supplier; |
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import junit.framework.AssertionFailedError; |
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import junit.framework.Test; |
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import junit.framework.TestSuite; |
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|
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if (!createIncomplete) assertTrue(f.complete(v1)); |
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final CompletableFuture<Integer> g = f.exceptionally |
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((Throwable t) -> { |
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// Should not be called |
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a.getAndIncrement(); |
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throw new AssertionError(); |
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threadFail("should not be called"); |
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return null; // unreached |
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}); |
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if (createIncomplete) assertTrue(f.complete(v1)); |
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* whenComplete action executes on normal completion, propagating |
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* source result. |
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*/ |
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< |
public void testWhenComplete_normalCompletion1() { |
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> |
public void testWhenComplete_normalCompletion() { |
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for (ExecutionMode m : ExecutionMode.values()) |
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for (boolean createIncomplete : new boolean[] { true, false }) |
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for (Integer v1 : new Integer[] { 1, null }) |
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* If a whenComplete action throws an exception when triggered by |
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* a normal completion, it completes exceptionally |
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*/ |
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< |
public void testWhenComplete_actionFailed() { |
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> |
public void testWhenComplete_sourceCompletedNormallyActionFailed() { |
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for (boolean createIncomplete : new boolean[] { true, false }) |
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for (ExecutionMode m : ExecutionMode.values()) |
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for (Integer v1 : new Integer[] { 1, null }) |
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if (!testImplementationDetails) return; |
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Function<Method, String> toSignature = |
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(method) -> method.getName() + Arrays.toString(method.getParameterTypes()); |
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Predicate<Method> isNotStatic = |
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(method) -> (method.getModifiers() & Modifier.STATIC) == 0; |
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List<Method> minimalMethods = |
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Stream.of(Object.class, CompletionStage.class) |
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.map((klazz) -> Stream.of(klazz.getMethods())) |
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.reduce(Stream::concat) |
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.orElseGet(Stream::empty) |
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.filter((method) -> (method.getModifiers() & Modifier.STATIC) == 0) |
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.flatMap((klazz) -> Stream.of(klazz.getMethods())) |
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.filter(isNotStatic) |
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.collect(Collectors.toList()); |
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// Methods from CompletableFuture permitted NOT to throw UOE |
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String[] signatureWhitelist = { |
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Stream.of(signatureWhitelist)) |
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.collect(Collectors.toSet()); |
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List<Method> allMethods = Stream.of(CompletableFuture.class.getMethods()) |
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.filter((method) -> (method.getModifiers() & Modifier.STATIC) == 0) |
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.filter(isNotStatic) |
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.filter((method) -> !permittedMethodSignatures.contains(toSignature.apply(method))) |
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.collect(Collectors.toList()); |
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|
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throw new Error("Methods did not throw UOE: " + bugs.toString()); |
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} |
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static class Monad { |
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static class ZeroException extends RuntimeException { |
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public ZeroException() { super("monadic zero"); } |
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} |
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// "return", "unit" |
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static <T> CompletableFuture<T> unit(T value) { |
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return completedFuture(value); |
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} |
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// monadic zero ? |
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static <T> CompletableFuture<T> zero() { |
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return failedFuture(new ZeroException()); |
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} |
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// >=> |
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static <T,U,V> Function<T, CompletableFuture<V>> compose |
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(Function<T, CompletableFuture<U>> f, |
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Function<U, CompletableFuture<V>> g) { |
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return (x) -> f.apply(x).thenCompose(g); |
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} |
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|
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static void assertZero(CompletableFuture<?> f) { |
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try { |
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f.getNow(null); |
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throw new AssertionFailedError("should throw"); |
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} catch (CompletionException success) { |
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assertTrue(success.getCause() instanceof ZeroException); |
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} |
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} |
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|
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static <T> void assertFutureEquals(CompletableFuture<T> f, |
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CompletableFuture<T> g) { |
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T fval = null, gval = null; |
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Throwable fex = null, gex = null; |
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|
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try { fval = f.get(); } |
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catch (ExecutionException ex) { fex = ex.getCause(); } |
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catch (Throwable ex) { fex = ex; } |
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|
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try { gval = g.get(); } |
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catch (ExecutionException ex) { gex = ex.getCause(); } |
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catch (Throwable ex) { gex = ex; } |
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|
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if (fex != null || gex != null) |
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assertSame(fex.getClass(), gex.getClass()); |
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else |
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assertEquals(fval, gval); |
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} |
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|
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static class PlusFuture<T> extends CompletableFuture<T> { |
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AtomicReference<Throwable> firstFailure = new AtomicReference<>(null); |
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} |
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|
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// Monadic "plus" |
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static <T> CompletableFuture<T> plus(CompletableFuture<? extends T> f, |
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CompletableFuture<? extends T> g) { |
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PlusFuture<T> plus = new PlusFuture<T>(); |
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BiConsumer<T, Throwable> action = (T result, Throwable ex) -> { |
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if (ex == null) { |
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if (plus.complete(result)) |
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if (plus.firstFailure.get() != null) |
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plus.firstFailure.set(null); |
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} |
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else if (plus.firstFailure.compareAndSet(null, ex)) { |
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if (plus.isDone()) |
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plus.firstFailure.set(null); |
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} |
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else { |
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// first failure has precedence |
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Throwable first = plus.firstFailure.getAndSet(null); |
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|
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// may fail with "Self-suppression not permitted" |
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try { first.addSuppressed(ex); } |
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catch (Exception ignored) {} |
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|
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plus.completeExceptionally(first); |
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} |
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}; |
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f.whenComplete(action); |
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g.whenComplete(action); |
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return plus; |
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} |
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} |
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|
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/** |
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* CompletableFuture is an additive monad - sort of. |
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* https://en.wikipedia.org/wiki/Monad_(functional_programming)#Additive_monads |
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*/ |
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public void testAdditiveMonad() throws Throwable { |
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Function<Long, CompletableFuture<Long>> unit = Monad::unit; |
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CompletableFuture<Long> zero = Monad.zero(); |
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|
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// Some mutually non-commutative functions |
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Function<Long, CompletableFuture<Long>> triple |
| 3858 |
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= (x) -> Monad.unit(3 * x); |
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Function<Long, CompletableFuture<Long>> inc |
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= (x) -> Monad.unit(x + 1); |
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// unit is a right identity: m >>= unit === m |
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Monad.assertFutureEquals(inc.apply(5L).thenCompose(unit), |
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inc.apply(5L)); |
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// unit is a left identity: (unit x) >>= f === f x |
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Monad.assertFutureEquals(unit.apply(5L).thenCompose(inc), |
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inc.apply(5L)); |
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// associativity: (m >>= f) >>= g === m >>= ( \x -> (f x >>= g) ) |
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Monad.assertFutureEquals( |
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unit.apply(5L).thenCompose(inc).thenCompose(triple), |
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unit.apply(5L).thenCompose((x) -> inc.apply(x).thenCompose(triple))); |
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|
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// The case for CompletableFuture as an additive monad is weaker... |
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|
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// zero is a monadic zero |
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Monad.assertZero(zero); |
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|
| 3879 |
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// left zero: zero >>= f === zero |
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Monad.assertZero(zero.thenCompose(inc)); |
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// right zero: f >>= (\x -> zero) === zero |
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Monad.assertZero(inc.apply(5L).thenCompose((x) -> zero)); |
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|
| 3884 |
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// f plus zero === f |
| 3885 |
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Monad.assertFutureEquals(Monad.unit(5L), |
| 3886 |
+ |
Monad.plus(Monad.unit(5L), zero)); |
| 3887 |
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// zero plus f === f |
| 3888 |
+ |
Monad.assertFutureEquals(Monad.unit(5L), |
| 3889 |
+ |
Monad.plus(zero, Monad.unit(5L))); |
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// zero plus zero === zero |
| 3891 |
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Monad.assertZero(Monad.plus(zero, zero)); |
| 3892 |
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{ |
| 3893 |
+ |
CompletableFuture<Long> f = Monad.plus(Monad.unit(5L), |
| 3894 |
+ |
Monad.unit(8L)); |
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// non-determinism |
| 3896 |
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assertTrue(f.get() == 5L || f.get() == 8L); |
| 3897 |
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} |
| 3898 |
+ |
|
| 3899 |
+ |
CompletableFuture<Long> godot = new CompletableFuture<>(); |
| 3900 |
+ |
// f plus godot === f (doesn't wait for godot) |
| 3901 |
+ |
Monad.assertFutureEquals(Monad.unit(5L), |
| 3902 |
+ |
Monad.plus(Monad.unit(5L), godot)); |
| 3903 |
+ |
// godot plus f === f (doesn't wait for godot) |
| 3904 |
+ |
Monad.assertFutureEquals(Monad.unit(5L), |
| 3905 |
+ |
Monad.plus(godot, Monad.unit(5L))); |
| 3906 |
+ |
} |
| 3907 |
+ |
|
| 3908 |
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// static <U> U join(CompletionStage<U> stage) { |
| 3909 |
|
// CompletableFuture<U> f = new CompletableFuture<>(); |
| 3910 |
|
// stage.whenComplete((v, ex) -> { |
