in src/main/java/com/spotify/futures/CompletableFutures.java [737:759]
public static <R, A, B, C, D, E, F> CompletionStage<R> combineFutures(
CompletionStage<A> a,
CompletionStage<B> b,
CompletionStage<C> c,
CompletionStage<D> d,
CompletionStage<E> e,
CompletionStage<F> f,
Function6<A, B, C, D, E, F, CompletionStage<R>> function) {
final CompletableFuture<A> af = a.toCompletableFuture();
final CompletableFuture<B> bf = b.toCompletableFuture();
final CompletableFuture<C> cf = c.toCompletableFuture();
final CompletableFuture<D> df = d.toCompletableFuture();
final CompletableFuture<E> ef = e.toCompletableFuture();
final CompletableFuture<F> ff = f.toCompletableFuture();
return CompletableFuture.allOf(af, bf, cf, df, ef, ff)
.thenCompose(ignored -> function.apply(af.join(),
bf.join(),
cf.join(),
df.join(),
ef.join(),
ff.join()));
}