Class Single

src/main/java/graphql/execution/Async.java:122–167

    }

    private static class Single<T> implements CombinedBuilder<T> {

        // avoiding array allocation as there is only 1 CF
        private Object value;
        private int ix;

        @Override
        public void add(CompletableFuture<T> completableFuture) {
            this.value = completableFuture;
            this.ix++;
        }

        @Override
        public void addObject(Object object) {
            this.value = object;
            this.ix++;
        }

        @Override
        public CompletableFuture<List<T>> await() {
            commonSizeAssert();
            if (value instanceof CompletableFuture) {
                @SuppressWarnings("unchecked")
                CompletableFuture<T> cf = (CompletableFuture<T>) value;
                return cf.thenApply(Collections::singletonList);
            }
            //noinspection unchecked
            return CompletableFuture.completedFuture(Collections.singletonList((T) value));
        }

        @Override
        public Object awaitPolymorphic() {
            commonSizeAssert();
            if (value instanceof CompletableFuture) {
                @SuppressWarnings("unchecked")
                CompletableFuture<T> cf = (CompletableFuture<T>) value;
                return cf.thenApply(Collections::singletonList);
            }
            //noinspection unchecked
            return Collections.singletonList((T) value);
        }

        private void commonSizeAssert() {
            Assert.assertTrue(ix == 1, () -> "expected size was " + 1 + " got " + ix);
        }
    }

    private static class Many<T> implements CombinedBuilder<T> {