How to use Java 8 Optionals, performing an action if all three are present?

Using a helper function, things at least become un-nested a little:

@FunctionalInterface
interface TriConsumer<T, U, S> {
    void accept(T t, U u, S s);
}

public static <T, U, S> void allOf(Optional<T> o1, Optional<U> o2, Optional<S> o3,
       TriConsumer<T, U, S> consumer) {
    o1.ifPresent(t -> o2.ifPresent(u -> o3.ifPresent(s -> consumer.accept(t, u, s))));
}

allOf(maybeTarget, maybeSourceName, maybeEventName,
    (target, sourceName, eventName) -> {
        /// ...
});

The obvious downside being that you'd need a separate helper function overload for every different number of Optionals

I think to stream the three Optionals is an overkill, why not the simple

if (maybeTarget.isPresent() && maybeSourceName.isPresent() && maybeEventName.isPresent()) {
  ...
}

In my eyes, this states the conditional logic more clearly compared to the use of the stream API.